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PubMed1996

Spectral analysis of blood pressure and heart rate, catecholamine and neuropeptide Y plasma levels in a new model of neurogenic orthostatic hypotension in dog.

The aim of the study was to compare changes in blood pressure (BP) and heart rate (HR) variability, catecholamine and neuropeptide Y (NPY) plasma levels induced by passive head-up tilt in normal and sino-aortic denervated (SAD) chloralose-anaesthetized dogs. In controls, 80 degrees head-up tilt test failed to change BP and increased HR. Plasma noradrenaline and NPY levels (but not adrenaline) significantly rose. In SAD dogs, head-up tilt test induced a marked and reproducible decrease in BP without any change in HR or noradrenaline and NPY plasma levels. In SAD dogs, spectral analysis in supine position was characterized by reduced variability in the high frequency (HF) band of the HR spectrum without changes in low frequency (LF) bands of both HR and systolic blood pressure (SBP). Head-up tilt test increased the LF component of SBP variability and decreased the HF component of HR variability in controls but failed to modify HR and BP variabilities in SAD dogs. In conclusion, sino-aortic denervation in dogs elicits a reproducible postural fall in BP with impaired adaptation of sympathetic nervous system activity. This model may be of value in evaluating the pharmacological effects of drugs for the management of orthostatic hypotension.

Adaptation, Physiological↗
PubMed1998

Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. II. Event-related synchronization in the gamma band.

It has been shown in animals that neuronal activity in the 'gamma band' (>30 Hz) is associated with cortical activation and may play a role in multi-regional and multi-modal integration of cortical processing. Studies of gamma activity in human scalp EEG have typically focused on event-related synchronization (ERS) in the 40 Hz band. To assess further the gamma band ERS further, as an index of cortical activation and as a tool for human functional brain mapping, we recorded subdural electrocorticographic (ECoG) signals in five clinical subjects while they performed visual-motor decision tasks designed to activate the representations of different body parts in sensorimotor cortex. ECoG spectral analysis utilized a mixed-effects analysis of variance model in which within-trial temporal dependencies were accounted for. Taking an exploratory approach, we studied gamma ERS in 10-Hz-wide bands (overlapping by 5 Hz) ranging from 30 to 100 Hz, and compared these findings with changes in the alpha (8-13 Hz) and beta (15-25 Hz) bands. Gamma ERS (observed in three out of subjects) occurred in two broad bands-'low gamma' included the 35-45 and 40-50 Hz bands, and 'high gamma' the 75-85, 80-90, 85-95 and 90-100 Hz bands. The temporal and spatial characteristics of low and high gamma ERS were distinct, suggesting relatively independent neurophysiological mechanisms. Low gamma ERS often began after onset of the motor response and was sustained through much of it, in parallel with event-related desynchronization (ERD) in the alpha band. High gamma ERS often began during, or slightly before, the motor response and was transient, ending well before completion of the motor response. These temporal differences in low and high gamma suggest different functional associations with motor performance. Compared with alpha and beta ERD, the topographical patterns of low and high gamma ERS were more discrete and somatotopically specific and only occurred over contralateral sensorimotor cortex during unilateral limb movements (alpha and beta ERD were also observed ipsilaterally). Maps of sensorimotor function inferred from gamma ERS were consistent with maps generated by cortical electrical stimulation for clinical purposes. In addition, different task conditions in one subject produced consistent differences in both motor response latencies and onset latency of gamma ERS, particularly high gamma ERS. Compared with alpha and beta ERD, the topography of gamma ERS is more consistent with traditional maps of sensorimotor functional anatomy. In addition, gamma ERS may provide complementary information about cortical neurophysiology that is useful for mapping brain function in humans.

Adult↗
PubMed1992

Spectral analysis of bubble sounds in decompressed guinea pigs.

Doppler ultrasonic monitoring was used to detect bubbles in sixteen guinea pigs subjected to a simulated air-dive profile of 9 ATA for 25 minutes. After completion of the decompression, eight subjects did not demonstrate any signs of decompression sickness (DCS), two developed paraplegia and six died. Under sedation, the Doppler ultrasonic bubble detector was placed precordially to record the bubble signals in both pre-dive and post-dive. The recorded signals were analyzed with a high resolution signal analyzer to compare changes between pre-dive and post-dive spectrograms. Bubble signals appeared in the frequency range between 0.64 +/- 0.02 KHz and 6.08 +/- 0.30 KHz. In terms of the net spectral level versus frequency areas (difference between pre-dive and post-dive spectrograms), the mean areas in the paraplegia group and the death group were significantly larger than those in the group without DCS. Therefore, we concluded that the spectral analysis may be an objective and quantitative adjunctive method to the interpretation of Doppler bubble signals.

Animals↗
PubMed1986

Gas-liquid chromatography and mass spectral analysis of mono-, di- and tricarboxylates as their tert.-butyldimethylsilyl derivatives.

A gas-liquid chromatographic (GLC) procedure is described which permits the baseline separation and quantitation of twenty saturated monocarboxylates, sixteen dicarboxylates (both alkanedioic and alkenedioic), and the tricarboxylates citrate and aconitate in a single GLC analysis. The carboxylic acids, as their tert.-butyldimethylsilylated derivatives, are readily separable on a SPB-1 (bonded) capillary column. Separation data on an OV-17 (bonded) capillary column and a SP-2250 packed column of these carboxylates, in addition to fifteen unsaturated carboxylates, are also given. The tert.-butyldimethylsilylation of carboxylic acids in their free or ammonium salt forms is accomplished in a single derivatization step with N-methyl-N-(tert.-butyldimethylsilyl)-trifluoroacetamide. Retention data and responses for all mono-, di- and tricarboxylic acids are given. Mass spectral analysis of all tert.-butyldimethylsilylated carboxylic acids is presented and each displays a prominent and characteristic [M-57] fragment ion.

Carboxylic Acids↗
PubMed1978

[Possibilities of utilizing integral topography, vectorometry and spectral analysis of the complexograms for the diagnosis of ischemic heart disease].

Three approaches to the study of electric and mechanical heart activity were used, which were significant in the diagnosis of various variants of ischemic heart disease. The method of integral topography proved most applicable in the diagnosis of microfocal myocardial infarction. Infarctions which were marked by a typical clinical picture and the corresponding laboratory data (changes in enzymes, leukocytosis, etc)., but could not be sufficiently revealed in the commonly applied 12 leads of the ECG, were successfully identified due to changes in the ST--T zones of the topogram. In the diagnosis of ischemic heart disease attended with disorders of hemodynamics it is advisable to apply the histogram method of identification on the basis of spectral analysis of the complexograms, ballistocardiograms, arteriovenous pulsograms, and phonooscillograms. This method may also be used to assess the stage of circulatory insufficiency. In preventive examination for detecting ischemic heart disease, its painless variants in particular, it is advantageous to use the method of vectorometry of the ECG in in orthogonal leads with the subsequent solution of the diagnostic discrimination polynomials on a computer.

Ballistocardiography↗
PubMed1996

Needle EMG of the human diaphragm: power spectral analysis in normal subjects.

Needle EMG of the diaphragm was performed in 43 diaphragms in 23 healthy volunteers. The mean +/- standard deviation for the median frequency (MF) of the power spectrum was 233.3 +/- 58.1 Hz. The MF increased with age and showed a negative correlation with the forced vital capacity (FVC), but there was no correlation with other anthropometric measures or the results of phrenic nerve conduction study. The higher MF in older subjects may be due to early recruitment of larger units. The negative correlation between MF and FVC is likely secondary to a lower level of contraction required for normal breathing in subjects with high FVC. The integrated EMG (iEMG) of each inspiration strongly correlated with the tidal volume and the duration of inspiration. Power spectral analysis of diaphragmatic EMG is feasible and reliable. It can be used to assess respiratory muscle fatigue and may help in the diagnosis of neuromuscular disorders affecting the diaphragm.

Adult↗
PubMed1996

Sympathetic hyperactivity in patients with vasospastic angina--assessment by spectral analysis of heart rate and arterial pressure variabilities.

The autonomic nervous system may play an important role in regulating coronary arterial tone. To evaluate the role of autonomic nervous activity in patients with vasospastic angina (VSA), we studied 10 VSA patients with patent coronary artery (mean; 56 yr, range; 44-66 yr) and 8 normal subjects (mean; 58 yr, range; 35-71 yr). ECG and arterial pressure were continuously recorded for 4 min in a supine position at 7:30 am, 10:30 am, and 4:30 pm. Low-frequency (LF; 0.04-0.15 Hz) and high-frequency (HF; 0.20 Hz) components of the beat-to-beat variabilities of the R-R interval (RRI) and systolic arterial pressure (SAP) were then estimated by autoregressive power spectral analysis. The LF-Normalized Power (LF-NP; [LF Power]/[Total Power]-[Direct Current Power]) of both the RRI and SAP variabilities were greater in VSA patients than in normal subjects (RRI: 0.51 +/- 0.07, 0.51 +/- 0.07, 0.53 +/- 0.06, vs 0.25 +/- 0.04, 0.31 +/- 0.05, 0.31 +/- 0.06, at 7:30 am, 10:30 am, and 4:30 pm respectively: p = 0.010, 0.044, 0.018. SAP: 0.62 +/- 0.06, 0.53 +/- 0.06, 0.57 +/- 0.06 vs 0.37 +/- 0.04, 0.30 +/- 0.06, 0.26 +/- 0.07, respectively: p = 0.006, 0.017, 0.003.). The LF-power of SAP variability also tended to be greater in VSA patients. There was no difference in the HF-component coefficient of variance (CCV (%) = 100 x (component power) (1/2)/ mean RR intervals) of the RRI variabilities between the 2 groups. These results indicate that increased sympathetic vasomotor tone and cardiac sympathetic predominance may play an important role in patients with VSA.

Adult↗
PubMed1999

Muscle metaboreflex contribution to sinus node regulation during static exercise: insights from spectral analysis of heart rate variability.

BACKGROUND: It is currently assumed that during static exercise, central command increases heart rate (HR) through a decrease in parasympathetic activity, whereas the muscle metaboreflex raises blood pressure (BP) only through an increase in sympathetic outflow to blood vessels, because when the metaboreflex activation is maintained during postexercise muscle ischemia, BP remains elevated while HR recovers. We tested the hypotheses that the muscle metaboreflex contributes to HR regulation during static exercise via sympathetic activation and that the arterial baroreflex is involved in the HR recovery of postexercise muscle ischemia. METHODS AND RESULTS: Eleven healthy male volunteers performed 4-minute static leg extension (SLE) at 30% of maximal voluntary contraction, followed by 4-minute arrested leg circulation (ALC). Autonomic regulation of HR was investigated by spectral analysis of HR variability (HRV), and baroreflex control of heart period was assessed by the spontaneous baroreflex method. SLE resulted in a significant increase in the low-frequency component of HRV that remained elevated during ALC. The normalized high-frequency component of HRV was reduced during SLE and returned to control levels during ALC. Baroreflex sensitivity was significantly reduced during SLE and returned to control levels during ALC when BP was kept elevated above the resting level while HR recovered. CONCLUSIONS: The muscle metaboreflex contributes to HR regulation during static exercise via a sympathetic activation. The bradycardia that occurs during postexercise muscle ischemia despite the maintained sympathetic stimulus may be explained by a baroreflex-mediated increase in parasympathetic outflow to the sinoatrial node that overpowers the metaboreflex-induced cardiac sympathetic activation.

Adult↗
PubMed1991

Night sleep electroencephalogram power spectral analysis in excessive daytime sleepiness disorders.

A group of 53 patients (40 males, 13 females) with mean age of 49 years, ranging from 30 to 70 years, was evaluated in the following excessive daytime sleepiness (EDS) disorders: obstructive sleep apnea syndrome (B4a), periodic movements in sleep (B5a), affective disorder (B2a), functional psychiatric non affective disorder (B2b). We considered all adult patients referred to the Center sequentially with no other distinctions but these three criteria: (a) EDS was the main complaint; (b) right handed; (c) not using psychotropic drugs for two weeks prior to the all-night polysomnography. EEG (C3/A1, C4/A2) samples from 2 to 10 minutes of each stage of the first REM cycle were chosen. The data was recorded simultaneously in magnetic tape and then fed into a computer for power spectral analysis. The percentage of power (PP) in each band calculated in relation to the total EEG power was determined of subsequent sections of 20.4 s for the following frequency bands: delta, theta, alpha and beta. The PP in all EDS patients sample had a tendency to decrease progressively from the slowest to the fastest frequency bands, in every sleep stage. PP distribution in the delta range increased progressively from stage 1 to stage 4; stage REM levels were close to stage 2 levels. In an EDS patients interhemispheric coherence was high in every band and sleep stage. B4a patients sample PP had a tendency to decrease progressively from the slowest to the fastest frequency bands, in every sleep stage; PP distribution in the delta range increased progressively from stage 1 to stage 4; stage REM levels were between stage 1 and stage 2 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

[Metrological aspects of the spectral analysis of cardiac rhythm].

There are factors (presence of slow waves with the period that exceeds the recording duration, nonmultiplicity of the analysed oscillation periods to realisation), which do not allow reliable and reproducible estimations of the spectrum parameters in the slow area even in case of the stable patient's state. In case there are oscillations in the heart rhythm with periods comparable with the recording duration application of such a well known method like the elimination of polynominal trend to inhibit destabilizing effect of the factors is not effective enough. To increase the reliability and reproducibility in estimating heart rhythm wave pattern, its registration should be carried out only in the stable patient's condition long enough to cover several periods of the slowest analysed waves, that will limit the applications of the heart rhythm spectral analysis in clinical practice.

Heart Rate↗
PubMed1988

Naloxone facilitates sensory precipitation of focal and generalized seizures: evoked potentials and power spectral analysis in the cat.

To analyze the role of endogenous opioids on epileptogenesis the effect of repeated doses of naloxone alone (NA) (2, 4, and 8 mg/kg every 15 min) or along with intermittent photic stimulation (NPS) (1, 3, and 10 Hz) was tested on acute "Encephale isolé" cats. The electrical activity recordings of sensorimotor cortex (SMC), visual cortex, and right and left amygdalae revealed progressive changes as naloxone was administered: (A) slow spindle activity (4-6 Hz) in SMC, (B) 12 Hz rhythmic activity in both amygdalae, (C) generalized paroxysms, and (D) spontaneous tonic-clonic electrographic seizures. These changes occurred in both experimental groups (NA, NPS), and their onset was dose-related. Photic stimulation precipitated these phenomena. The amplitude of the visual evoked potential components (N1-P1, P1-N2, N2-P2) and power spectral analysis of spontaneous and evoked activity underwent progressive changes. Our results confirm a facilitatory effect of naloxone on epileptogenesis and suggest a possible role of endogenous opioids in this process and on sensory pathways' excitability.

Amygdala↗
PubMed1975

EEG spectral analysis for the evaluation of the central effects of delta6-tetrahydrocannabinol in rabbits.

The effects of delta6-THC on the frequency spectrum of the hippocampal EEG were examined with the assistance of an electronic integrator. Six rabbits bearing chronically implanted cortical and hippocampal electrodes were dosed intravenously with delta6-THC (2.5 percent solution in polyethylene glycol 300; doses of 10, 50, 100, 250 and 1000 mug/kg) once a week. A comparison of epochs of arousal in the pre-drug control and post-drug periods demonstrated that a dose as low as 50 mug/kg produced a consistent, statistically significant diminution in "power" of the 7,8,9 Hz frequencies of the hippocampal EEG, with 8 Hz the most sensitive. Doses above 250 mug/kg produced an overall decrease in the "power" spectrum from 7 to 22 Hz. Spectral analysis of the EEG offers a method which is sufficiently sensitive to reveal a central effect of detla6-THC in rabbits at doses equivalent to the human threshold for psychic effects.

Animals↗
PubMed1991

[Prognostic value of spectral analysis of electroencephalogram in patients with severe head injury].

To determine the prognostic value of electroencephalogram (EEG) in patients with severe head injury, fifteen adult patients were examined for three months after trauma. All patients (age: 16-74 years old) remained comatose (Glasgow Coma Scale: less than 8) for more than 72 hours. Ten out of 15 cases were surgically treated. Barbiturates were not used in any patient for the sake of controlling the increased intracranial pressure. Three months after trauma, the clinical outcome of each patient was evaluated using Glasgow Outcome Scale (GOOD: good recovery/moderate disability, POOR: severe disability/persistently vegetative/dead). EEG was examined repeatedly for 3 months after trauma; 56 EEG recordings were performed on 15 cases. Each EEG recording was never for less than 12 hours and EEG was recorded from the bilateral parietal electrodes. Using EEG TREND MONITOR (NIHONKODEN), the spectral analysis of EEG was performed in five frequency bands (delta, theta, alpha-1, alpha-2, beta) and the EEG power of each frequency band was shown as the percentage of total EEG power (% FREQ BAND). The findings of each % FREQ BAND was classified into the following four groups. 1) slow-monotonous: The EEG power was comprised invariably and almost exclusively of low frequency bands (i.e. delta and theta), and the "slow-fast constant" which is the power of slow waves (delta and theta) divided by the power of fast waves (alpha-1, alpha-2, and beta) was stable.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1996

Twenty-four-hour pattern of blood pressure and spectral analysis of heart rate variability in diabetic patients with various degrees of autonomic neuropathy. Comparison to standard cardiovascular tests.

We performed four cardiovascular tests of autonomic function (deep breathing, lying to standing, Valsalva manoeuvre, postural hypotension) and simultaneous 24h recordings of blood pressure (BP) and ECG in 35 normotensive diabetic subjects. Autoregressive power spectrum analysis of RR interval variability was applied to 24h ECG recordings to obtain for day and night periods power of low- (0.03-0.15 Hz, LF) and high-frequency (0.18- 0.40 Hz, HF) components, relative markers of sympathetic and vagal activity respectively, and their ratio (LF/HF), assumed as index of sympathovagal balance. Eighteen patients showed normal cardiovascular tests, 6 patients one abnormal heart rate test, 5 patients two abnormal heart rate tests, and 6 patients also abnormal postural hypotension test. In diabetic patients with increasing degree of autonomic neuropathy, there was a progressive reduction of day-night change in systolic BP (p < 0.01), of LF during the day (p < 0.01), of HF during the night (p < 0.04), of day-night change in HF (p < 0.02), and of day-night change in HF/LF (p < 0.03). Day-night change in systolic BP was related to postural hypotension (p < 0.001) and to deep breathing (p < 0.01). Day LF was related to lying to standing (p < 0.001), to postural hypotension (p < 0.005) and to deep breathing (p < 0.007). Night HF was related to deep breathing (p < 0.0002) and to lying to standing (p < 0.02). Day-night change in HF/LF was slightly related to deep breathing, lying to standing, and to postural hypotension (p < 0.04). In a multiple regression analysis including age, diabetes duration, and cardiovascular tests as independent variables, day-night change in BP and day LF were only related to postural hypotension, whereas night HF was related to deep breathing. In conclusion, in diabetic patients with increasing autonomic damage, there is a progressive impairment of nocturnal fall of BP and of sympathetic activity during the day, blunted nocturnal increase of vagal activity and lower circadian variation in sympathovagal balance. The significant but not very close correlation of day-night pattern of BP and sympathovagal activity to standard cardiovascular reflex tests, supports the independent usefulness of 24h BP monitoring and spectral analysis of heart rate variability in diabetic neuropathy.

Adult↗
PubMedDate not supplied

[Spectral analysis of nucleotide sequences].

The data of Fourier-analysis of nucleotide sequences are discussed. The existence of reflexes corresponding to regular position of nucleotides (mainly T and G) with 3-base period is the most striking feature of both phage and viral nucleic acid sequences spectra. The amplitude and phase of the similar reflexes in the dinucleotide spectra obtained by digital computing of Fourier-transform, give specific information on amino acid composition, codon bias, amino acid relations. The width of frequency band characterizes a tendency to nucleotide clustering or to separate existence. The blurring of reflexes shows the disturbance of far order in the regular nucleotide "lattice". The two-dimensional spectral analysis supports the existence of far correlation in nucleotide positions.

Base Sequence↗
PubMed1986

Spectral analysis of dual jerk waveforms in congenital nystagmus.

Congenital nystagmus (CN) is a disorder of the ocular motility characterized by oscillatory eye movements preventing the correct fixation of a target. Many typical waveforms of eye position recordings have been recognized and classified in the literature: in jerk CN a slow phase eye movement is followed by a fast phase, giving rise to a typical saw-tooth waveform, while in pendular CN the eyes exhibit a periodic motion, giving rise to an approximately sinusoidal waveform. Dual jerk waveforms seemed to show small, rapid oscillations superimposed on a jerk-like wave-form, thus being originally classified as a mixture of jerk and pendular CN. On the contrary, a theoretical model of CN has appeared recently, which suggests a possible interpretation of the small amplitude oscillations in dual jerk waveforms as consecutive pieces of growing and decaying exponentials. By spectral analysis of dual jerk waveforms in a number of patients with CN, we show that the oscillations are truly sinusoidal in nature, thus suggesting the possibility of a different explanation of dual jerk waveforms in CN.

Adolescent↗
PubMed1998

[Electromyographic power spectral analysis of sternocleidomastoid muscle during sustained voluntary clenching].

The purpose of this study was to investigate the changes of the activity of the sternocleidomastoid (SCM) muscles during sustained voluntary clenching. Ten healthy male subjects without any occlusal functional problems were asked to clench as long as possible in the intercuspal position while keeping the electromyographic activity of the masseter muscle at the 50% maximum voluntary contraction. Frequency analysis was carried out by computer using a fast Fourier transform algorithm to obtain the power spectrum of the SCM muscle during the fatiguing process and the recovery process. The results were as follows: 1. Sustained activities of the SCM muscles were observed during sustained voluntary clenching. 2. The power spectra of the SCM muscles significantly shifted to a lower frequency as time elapsed. 3. The power spectra of the SCM muscles obtained three minutes after relaxation recovered to those of the beginning of clenching. These findings indicated that muscle fatigue may be induced in the SCM muscle during sustained voluntary clenching and that electromyographic power spectral analysis can be used as a noninvasive, objective, and quantitative index of SCM muscle fatigue.

Adult↗
PubMedDate not supplied

Spectral analysis of heart rate variability: an emerging tool for assessing stability during transition to extrauterine life.

Transition from fetal to neonatal life is likely the most physiologically demanding time of life. Complex changes in major organ system functioning and reorganization of metabolic processes must occur rapidly to achieve postnatal homeostasis. Identifying the neonate with subtle signs of unsuccessful transition is a challenge to the perinatal health care provider. Alterations in fetal or neonatal heart rate and heart rate variability may serve as an indicator of the neural control influencing cardiac function and a sensitive indicator of compromised health. Evaluation of the neural control of the heart can be done noninvasively and provides a discriminating measure of the level of stress vulnerability the fetus or newborn may be experiencing. This article reviews the origins of physiological variability of the fetal and neonatal heart rate in the transition to extrauterine life. The technique of spectral analysis as a new tool for surveillance of the at-risk fetus and neonate is then introduced, and implications for clinical practice and future research avenues are discussed.

Adaptation, Physiological↗