Spectral analysis of the cardiac rhythm of fishes

Spectral analysis of the rhythmograms in the cod Gadus morhua callarias, plaice Pleuronectes platessa, herring Clupea harengus membras and trout Salmo gairdneri revealed complex wave structure of their cardiac rhythm. In all the species investigated, slow (0.01-0.06 Hz), intermediate (0.06-0.25 Hz) and fast (0.25-0.5 Hz) waves were recorded. It is suggested that the wave structure of cardiac rhythm reflects rather complicated relationships between functional systems regulating cardiac activity.     

Treatment of a depressive disorder patient with EEG-driven photic stimulation

This study examined the effects of electroencephalographic-(EEG-) driven photic stimulation on a case of depressive disorder, as measured by a psychometric test of mood states, EEG parameters, and several autonomic indices. The EEG-driven photic stimulation enhances the alpha rhythm of brain waves using photic signals, the brightness of which is modulated by a subject's own alpha rhythm. The patient was a 37-year-old businessman, who was treated for depression with medication during the 13 months prior to his first visit to our hospital. He underwent two sets of inpatient treatment sessions, comprising first 16 and then 18 treatment sessions. The treatments brought about the following changes: an improvement in general mood state, alpha rhythm increase, cardiac parasympathetic suppression, and increased skin conductance level. In addition, significant correlations between alpha rhythm increase and cardiac parasympathetic suppression or cardiac sympathetic predominance were observed with each inpatient treatment. Significant correlations between alpha rhythm increase, cardiac parasympathetic suppression, or cardiac sympathetic predominance and the improvement of general mood state were also observed. Thus, from these observations, it was concluded that the alpha enhancement induced by EEG-driven photic stimulation produced an improvement in the patient's depressive symptomatology connected with cardiac parasympathetic suppression and sympathetic predominance.     

A Minimal Model for the Respiratory Sinus Arrhythmia

The cardiac and respiratory rhythms in humans are known to be coupled by several mechanisms. In particular, the first rhythm is deeply modulated by the second. In this report we propose a simple operational model for heart rate variability which, taking such modulation into account, reproduces the main features of some experimental sequences of RR intervals recorded from healthy subjects in the resting condition. Also, peer analysis of the model performance allows us to answer the question whether the observed behaviour should be ascribed to phase synchronisation of the heart beating to the respiratory rhythm. Lastly, the changes of the model activity brought about by changing its relevant parameters are analysed and discussed     

Change of Parameters of Functioning of the Cardiovascular and Respiratory Systems in Rats of Different Ages under Effects of Low Doses of the Cholinesterase Inhibitor Phosphacol

In the 4-day old rat pups and adult animals there were studied effects of subacute and acute phosphacol intoxication at the doses producing and not producing inhibition of aetylcholinesterase on ECG parameters and respiration rate. Analysis of the heart rhythm variability (HRV) was performed using an original program designed in the Labview media. The frequency diapason of cardiointervals was divided as follows: the high-frequency component (HF)-0.8-2.5 Hz, the low-frequency (LF, waves of the II order)-0.8-0.3 Hz; frequencies lower than 0.3 Hz-VLF (slow waves of the III order). Under the conditions of the subacute intoxication the heart rate frequency in the 4-day old and in adult rats increases by 36% and 13%, respectively, the respiration rate frequency increases by 73% in the newborn and does not change in adult rats. The VHR analysis indicates an increase of the tone of the parasympathetic nervous system. The level of the sympathetic activity somewhat increases in adults, but decreases in the 5-day old rat pups, which leads to an essential shift of the vagosympathetic balance towards predominance of parasympathetic influences. In adult rats, unlike the newborns, the role of the humoral-metabolic factors in regulation of the cardiac rhythm and vasomotor reactions increases significantly. Remarkably, the decrease of the nervous sympathetic effects in the rat pups leads to the positive chronotropic effect and stabilization of the cardiac rhythm. Acute phosphacol intoxication (doses of 0.25 and 1 µg/kg) is studied in the 4-day old rat pups. The low dose of the drug leads to development of a moderate bradycardia without disturbances of the cardiac rhythm. The high phosphacol dose produces pronounced bradycardia; on its background there develops a long-term transitory arrhythmia representing complexes of the heart rhythm, which alternate in the decasecond or nearminute rhythm and are separated by periodicity that is one order slower. We observed such rhythm earlier during activation of central N-cholinoreactive structures and development of bilateral pneumothorax. Results of the present study allow stating the paradoxical heart rhythm not as agonic, non-peculiar to the “living” organism, but as a special form of functioning of cardiac pacemakers due to disturbances of the heart regulatory mechanism.__________Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 2, 2005, pp. 160–167.Original Russian Text Copyright © 2005 by Kuznetsov, Goncharov, Glashkina.     

Alterations of the characteristics of the circadian rest-activity rhythm of cancer in-patients

The aim of the present study was to evaluate the characteristics of the circadian rest-activity rhythm of cancer patients. Thirty-one in-patients, consisting of 19 males and 12 females, were randomly selected from the Regional Cancer Center, Pandit Jawaharlal Nehru Medical College, Raipur, India. The rest-activity rhythm was studied non-invasively by wrist actigraphy, and compared with 35 age-matched apparently healthy subjects (22 males and 13 females). All subjects wore an Actiwatch (AW64, Mini Mitter Co. Inc., USA) for at least 4-7 consecutive days. Fifteen-second epoch length was selected for gathering actigraphy data. In addition, several sleep parameters, such as time in bed, assumed sleep, actual sleep time, actual wake time, sleep efficiency, sleep latency, sleep bouts, wake bouts, and fragmentation index, were also recorded. Data were analyzed using several statistical techniques, such as cosinor rhythmometry, spectral analysis, ANOVA, Duncan's multiple-range test, and t-test. Dichotomy index (I相似文献   

Control of the circadian rhythm of locomotor activity in the house cricket

A detailed analysis was made of the locomotor activity of Acheta domesticus under conditions of 12 hr light and 12 hr darkness (LD 12 : 12) and of continuous darkness (DD). Under LD 12 : 12 it was found that there are three types of insects: (1) those beginning the period of increased locomotor activity immediately after darkness falls, (2) considerably before this time, and (3) considerably after this time. Under DD conditions the greater amount of the insects have a free-running rhythm shorter than 24 hr, while only a small percentage have a rhythm of more than 24 hr.Destruction of the neurosecretory cells of the pars intercerebralis by means of radio waves leads to the formation of hyperactivity and loss of locomotor activity rhythm when more than half of these cells are destroyed.Injection of reserpine into the insect's haemolymph with doses of 10 μg/g of body weight results in a reduction in locomotor activity and produces arrhythmicity for 2 to 3 days under LD 12 : 12 conditions. Under DD conditions, however, this same dose results in a total and irretrievable loss of free-running rhythm. Histological studies of the brain of crickets following injection of reserpine show a large degree of accumulation of neurosecretion in the cells of the pars intercerebralis as compared with control insects.A hypothesis is put forward as to the way in which the brain centres regulating locomotor rhythm act in crickets.     

Exposure to strong ELF magnetic fields does not alter cardiac autonomic control mechanisms

Clinical and epidemiological studies attest that alterations in heart rate variability (HRV) are predictive of specific types of cardiovascular morbidity and mortality in otherwise healthy persons. Recent reports also suggest that changes in HRV may be associated with exposure to intermittent magnetic fields (60 Hz, 28.3 microT) in the laboratory and that mortality is increased in cardiac disease categories related to altered HRV for utility workers whose jobs involve longer exposure to elevated magnetic fields. This study combined three approaches to learn more about the specific exposure circumstances under which changes in HRV occur. First, cardiac autonomic control, as indexed by HRV spectral analysis measures, was measured in 24 men during exposure to a much higher intensity field than any previously examined (resultant flux density = 127.3 microT [1273 milliGauss, mG]). Second, HRV measures from the same individual were compared across three relevant test conditions: intermittent and continuous field exposure and during a no-exposure, control condition. Third, electrocardiographic data were analyzed to determine if the precise timing of when the magnetic field switched on or off in relation to the cardiac cycle results in phase-resetting of the human cardiac rhythm. HRV measures were not altered by either field exposure condition compared to the control condition, and no evidence for a phase-resetting mechanism was found. Further research is needed to resolve the differences between the present and the earlier laboratory-based studies of HRV and to determine if cardiac rhythm disturbances are associated with exposure to the more complex magnetic fields found in the man-made environment.     

Circadian Rhythm of Gastric Acid Secretion in Active Duodenal Ulcer: Chronobiological Statistical Characteristics and Comparison of Acid Secretory and Plasma Gastrin Patterns with Healthy Subjects and Post-Vagotomy and Pyloroplasty Patients

Twenty-one male patients with active duodenal ulcer underwent hourly 24-hr gastric acid collections under controlled, calorically deprived conditions. The 24-hr hourly acid secretory output for the group displayed a statistically significant (p < 0.001) rhythm, with peak rates occurring during the evening hours and low rates during the early morning hours, by population-mean cosinor statistical analysis. Population-mean cosinor analysis also verified the occurrence of a significant (p=0.034) circadian rhythm in unstimulated acid secretion in a group (N=14) of healthy male subjects similarly studied and reported previously. In contrast, population-mean cosinor analysis confirmed the absence of any detectable circadian rhythm in unstimulated acid secretion in a group (N=17) of post-vagotomy and pyloroplasty patients studied 2-11 years after surgery. Population-mean cosinor analysis of 4-hr plasma gastrin determinations, obtained in all groups during the 24-hr gastric acid collection, revealed an absence of any detectable circadian rhythm in plasma gastrin. This latter finding is compatible with the interpretation that the circadian rhythm of unstimulated gastric acid secretion, observed in the clinically healthy and active ulcer groups, is unrelated to changes in plasma gastrin levels. The employment of quantitative chronobiological inferential statistical techniques is important to the analysis of any time-dependent measurement in gastrointestinal function, of which gastric acidity is one example.     

Circadian rhythm of gastric acid secretion in active duodenal ulcer: chronobiological statistical characteristics and comparison of acid secretory and plasma gastrin patterns with healthy subjects and postvagotomy and pyloroplasty patients

Twenty-one male patients with active duodenal ulcer underwent hourly 24-hr gastric acid collections under controlled, calorically deprived conditions. The 24-hr hourly acid secretory output for the group displayed a statistically significant (p less than 0.001) rhythm, with peak rates occurring during the evening hours and low rates during the early morning hours, by population-mean cosinor statistical analysis. Population-mean cosinor analysis also verified the occurrence of a significant (p = 0.034) circadian rhythm in unstimulated acid secretion in a group (N = 14) of healthy male subjects similarly studied and reported previously. In contrast, population-mean cosinor analysis confirmed the absence of any detectable circadian rhythm in unstimulated acid secretion in a group (N = 17) of postvagotomy and pyloroplasty patients studied 2-11 years after surgery. Population-mean cosinor analysis of 4-hr plasma gastrin determinations, obtained in all groups during the 24-hr gastric acid collection, revealed an absence of any detectable circadian rhythm in plasma gastrin. This latter finding is compatible with the interpretation that the circadian rhythm of unstimulated gastric acid secretion, observed in the clinically healthy and active ulcer groups, is unrelated to changes in plasma gastrin levels. The employment of quantitative chronobiological inferential statistical techniques is important to the analysis of any time-dependent measurement in gastrointestinal function, of which gastric acidity is one example.     

Circadian rhythm of airways caliber and its autonomic modulation

ABSTRACT

The autonomic nervous system (ANS) is one of the effector pathways for circadian variation of many physiological parameters. Autonomic tone and airways caliber have been reported to exhibit circadian variation in separate studies. A simultaneous investigation of heart rate variability (HRV) and airway caliber might ascertain how airway caliber is modulated by autonomic tone. This study was planned to identify the variations in airway caliber and autonomic function tone during a 24-hour span. A total of 56 healthy male subjects with almost similar daily routines were studied. Time domain, frequency domain and nonlinear analysis of R-R interval from 5 min electrocardiogram (ECG) was done seven times during the daytime wake span at 3-hour intervals starting at 05:00 h in the morning until 23:00 h in the night. Simultaneously peak expiratory flow rate (PEFR) was determined using a mini Wright’s peak flow meter. Rhythmometric analysis was done for PEFR and HRV parameters. Significant circadian variation in low frequency (LF) and high frequency (HF) variance was identified in this group of healthy subjects. The circadian rhythm of LF variance was characterized by a gradual increase and corresponding reciprocal change in HF variance from morning until night. The LF/HF ratio and SD2/SD1 ratio reflecting sympatho-vagal balance showed low to high values from morning to evening. The acrophase of the PEFR temporal pattern is similar to that of LF power and almost opposite in phase to that of HF power. PEFR is positively correlated with LF power. The circadian rhythm of airway caliber co-varies with cardiac autonomic tone. It appears that the temporal pattern of cardiac autonomic tone precedes in time that of airways caliber, thereby suggesting the latter operates under the modulatory effect of the 24-hour pattern in sympatho-vagal balance.     

Dynamics of cardiac rhythm in the transitional period during controlled physical exercises in persons of various ages

The transitional cardiac rhythm processes of work-in and recovery under standard dynamic loads of 25 and 50 W were studied in 90 healthy people aged 20-89 and in 15 elderly people being trained for endurance. The rhythmographic method was used for that purpose. Duration of the transitional processes (work-in and recovery) was revealed to considerably increase with age, while the cardiac rhythm increment--to decrease within the first 10 seconds of the work-in period. The data obtained suggest a worsened quality of the cardiac rhythm regulation in the transitional periods during aging, that is a result of an impairment of the vegetative influences on the sinoatrial node.     

经颈静脉途径制备Beagle犬心脏记忆模型

目的经颈静脉途径应用心室起搏的方法制备心脏记忆犬模型。方法 8只普通级成年健康Beagle犬经腹腔麻醉后,Seldinger’s法穿刺颈外静脉成功后送入心内膜起搏电极,将电极头端固定于右室心尖部,近端连接于脉冲发生器。起搏频率设置较犬窦性心律时的基础心率快15%,保证起搏器连续起搏。结果连续起搏1周后所有动物均成功制备为心脏记忆模型。建模后犬的心率、呼吸、体重与建模前比较,无明显改变;所有模型组犬起搏前心电图均为窦性心律,起搏1周后出现心脏T波记忆,在下壁导联以及胸前导联均出现T波倒置,停止起搏后,心脏T波记忆逐渐消失;模型组犬与正常组犬心肌病理相比,无明显改变。结论经颈静脉途径应用心室起搏法建立心脏记忆犬模型的方法,具有手术简单,创伤小,诱发方式与临床相似等优点,为深入展开心脏记忆的机制研究奠定基础。     

A period of urgent postnatal adaptation as a critical stage of human ontogenesis

The infant's state immediately after delivery is characterized by critical shifts of homeostasis parameters: decompensated mixed acidosis, pathologic indices of gaseous blood condition (arterial hypoxemia and hypercapnia), spontaneous postnatal hypothermia. Qualitative change of functional systems after delivery is accompanied by expressed tense of adaptation and regulation mechanisms and by centralization of cardiac rhythm control. The use of mathematical analysis of cardiac rhythm made it possible to find out that the change of degree of adaptation tense in the process- of postnatal period obeys the exponential dependence; moreover, the duration of transitional process of healthy newborns is 1 hour, but it considerably increases in case of hypoxia. After comparison of cardiac rhythm indices of these two groups of newborns it has been pointed out that mechanisms of adaptation after delivery are equal and they are based on the growing activity of central regulation processes. The dynamics of transitional process such as the period of postnatal adaptation indicates the reserve possibilities of infant and helps to reveal pre-nosological forms of disadaptational syndrome.     

Cardiac Rhythm Variability: Approaches to Mechanisms

Physiological mechanisms of cardiac rhythm variability (CRV) are reviewed. The results of original experiments are discussed together with the history of the problem and data available from the literature. Special emphasis is placed on the spectral analysis of cardiac rhythm. Various mechanisms of the generation of periodic and aperiodic components of CRV are considered. Although the variability of cardiac rhythm has been studied for many years in many laboratories worldwide, fine mechanisms of CRV remain obscure. However, a number of specific features of CRV are presently widely recognized. Periodic CRV components isolated from short-term records in patients at rest are represented by high-frequency, low-frequency, and very low-frequency oscillations. Fourier-transform spectral analysis of cardiac rhythm is the most appropriate method of the detection of these oscillations. High-frequency components are associated with respiration and represent the effects of the parasympathetic nervous system on myocardium. Low-frequency components are due to the activity of the postganglionic sympathetic fibers and represent the processes of cardiac rhythm modulation by the sympathetic nervous system. Genesis of very low-frequency oscillations is still uncertain. Most probably, these oscillations are associated with the effects of suprasegmental (primarily, hypothalamic) centers of autonomic regulation. Aperiodic CRV components represent random events associated with the reflex regulation of the heart rate by external or internal factors. Because aperiodic components significantly modify the results of the CRV analysis, the effects of these factors should be eliminated. It is concluded that because many problems associated with cardiac rhythm variability remain to be solved, extensive research in this direction should be continued.     

MHPG circadian rhythmicity in blood of healthy subjects

An earlier study showed that plasma concentrations of total 3-methoxy-4-hydroxyphenylglycol (MHPG), the major metabolite of norepinephrine, display a circadian rhythm in 6 male healthy subjects. In the previous study, the period of the rhythm was not fixed to 24 h thereby undermining the reliability of the cosinor parameter estimates. The present study extends the findings to a larger group of 12 clinically healthy male volunteers. Plasma total MHPG concentrations were determined every 3h for one full day. The data were fitted to a cosinor model fixing the period of the putative MHPG rhythm at 24 h. Several estimation techniques were utilized including Fourier analysis and time domain analysis with 4 variations. It is concluded that a circadian rhythm indeed characterizes MHPG blood concentrations. The concordance among the various parameter estimates is discussed.     

Multistability property in cardiac ionic models of mammalian and human ventricular cells

The underlying mechanisms of irregular cardiac rhythms are still poorly understood. Many experimental and modeling studies are aimed at identifying factors which cause cardiac arrhythmias. However, a lack of understanding of heart rhythm dynamical properties makes it difficult to uncover precise mechanisms of electrical instabilities, and hence to predict the onset of heart rhythm disorders. We review and compare the existing methods of studying cardiac dynamics, including restitution protocol (S1-S2), dynamic restitution protocol and multistability test protocol (S1-CI-S2). We focus on cardiac cell dynamics to elucidate regularities of heart rhythm. We demonstrate the advantages of our newly proposed systematic approach of analysis of cardiac cell dynamics using mammalian Luo Rudy 1991 and human ventricular Ten Tusscher 2006 single cell models under healthy and diseased conditions such as altered K⁺ or Ca²⁺ related currents. We investigate the role of ionic properties and the shape of an action potential on the nonlinear dynamics of electrical processes in periodically stimulated cardiac cells. We show the existence of multistability property for human ventricular cells. Moreover, the multistability is proposed to be an intrinsic property of cardiac cells, and is also suggested to be one of the mechanisms which could underlie the sudden triggering of life-threatening ventricular arrhythmias in the human heart.     

Circadian expression of connexins in the mouse heart

Significant circadian variations exist in the frequency of cardiac arrhythmia; however, the underlying mechanism is largely unknown. Connexins are essential in the propagation of electrical activity throughout the heart and are an important determinant of conduction velocity. Their dysfunction is related to the genesis of cardiac arrhythmia. In this study, we investigated if cx40 and cx43 expressed circadianly in the mouse heart using suprachiasmatic nuclei (SCN) lesion and pharmacological autonomic nervous system block mouse. Significant 24-h variations were observed in the expression of cx40 and cx43 in the sham-operated mice. In the SCNX mouse, all genes examined lost circadian rhythm. In the ANSB mouse, the expressions of Bmal1 was dampened significantly but still had circadian rhythm, whereas the two connexin gene expressions lost rhythm. These results suggest that cx40 and cx43 gene expressions have clear circadian rhythm and might be regulated by the central clock in the SCN through the ANS.     

Slow-wave fluctuations in craniosacral space: hemo-liquorodynamic conception of origin

In the paper, the mechanism of forming of rhythmic slow-wave fluctuations in craniospinal cavity was investigated. In five young healthy persons, at rest and under voluntary respiration arrest test, the bioimpedansograms of head and lumbosacral part of vertebral column were synchronously registered as these recordings reflect the changes of relationships between blood/CSF volumes in cranial and lumbosacral regions, respectively. The recordings were subjected to frequency and spectral computer analysis (PC Macintosh G-4, Chart 5.2. software). The rapid (pulsatile) as well as slow and counter-directed waves (frequency 6-10 cycles/min) of these processes were revealed in cranial and lumbosacral regions. The data obtained suggest the CSF dynamic concept of origin of the craniosacral rhythm. The pulse and slow-frequency oscillations of the cerebral vessels tone initiate corresponding intracranial pressure waves, and the latter are the motivating forces for to-and-fro CSF shifts in caudal direction. This mechanism is accompanied by tonic contractions of lumbar muscles and sacrum movements, and it is manually perceptible as a craniosacral rhythm.