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At least 613 records · Page 34Linked to original sources
PubMed2001

Modified autonomic balance in offsprings of diabetics detected by spectral analysis of heart rate variability.

This study was performed to evaluate the influence of family history for non-insulin-dependent diabetes mellitus (NIDDM) on autonomic balance. The latter was assessed by spectral analysis of heart rate variability (SA-HRV) and by analyzing the relative contribution of low-frequency (LF) and high-frequency (HF) components. Twenty glucose normotolerant offsprings of NIDDM parents and 20 controls underwent a 1-hour continuous electrocardiogram (ECG). LF and HF (mean +/- SEM in normalized units [NU]), respectively increased and decreased in offspring versus controls. The LF/HF ratio (mean +/- SEM) significantly increased (LF/HF = 3.25 +/- 0.7 v 1.45 +/- 0.5, P <.0001 offsprings v controls). To test a stimulated response, a passive tilting (+ 90 degrees ) after 30 minutes of bed rest (0 degrees ) was performed in a subsample of subjects (10 offsprings v 10 controls). During bed rest, we found significantly higher values of the LF/HF ratio in offsprings versus controls (1.93 +/- 0.3 v 1.08 +/- 0.2, P <.05), whereas in the head-up position, the LF/HF ratio value increased to the same levels in the 2 groups (6.48 +/- 1.3 v 6.89 +/- 1.4, not significant [NS]). NIDDM family history is characterized in the basal condition by an imbalance of the autonomic system, which, compared with controls, is expressed by a higher weight of sympathetic and a lower weight of parasympathetic components. No significant differences can be found under stimulated conditions.

Adult↗
PubMed1998

Spectral analysis of heart rate variability during desflurane and isoflurane anaesthesia in patients undergoing arthroscopy.

BACKGROUND: We studied the effect of desflurane (DES) and isoflurane (ISO) on heart rate variability (HRV) using power spectral analysis (PSA) of RR-interval in 30 patients undergoing arthroscopy, prior to induction, during anaesthesia and up to 3 h of recovery. PSA can distinguish low-frequency (LF) component and respiratory sinus arrhythmia (RSA) that are known to reflect predominantly sympathetic and parasympathetic activity, respectively. METHODS: After premedication with diclofenac and midazolam the anaesthesia was induced with propofol and maintained during spontaneous ventilation with either DES or ISO added to a mixture of nitrous oxide and oxygen. ECG and transthoracic impedance respirometer data were recorded. Power spectra were calculated with an autoregressive modelling method. RESULTS; Total power (PTOT) and individual power in two frequency bands of the HRV spectrum (PLF, 0.05-0.15 Hz and PRSA) decreased after induction of anaesthesia in both groups. At 60, 120 and 180 min of recovery the PTOT was back to control-value in the DES group but remained reduced in the ISO group. Calculated as normalised units, the PLF (nPLF) predominated over the PRSA (nPRSA) during control situations and during recovery. The reverse was the case during maintenance of anaesthesia. Thirty minutes after induction and during surgical stress the ISO group showed higher heart rate compared to the DES group as well as compared to control. CONCLUSION: DES and ISO produced similar alterations in studied parameters during the maintenance of anaesthesia. The differences observed between the groups during recovery may indicate an early intact neural reflex control system among the subjects exposed to DES. These results suggest that DES and ISO reduce the total autonomic neural system activity and alter the balance between sympathetic and parasympathetic activities in a comparable way during maintenance of anaesthesia. A more rapid recovery phase among the subjects exposed to DES is linked to differences in pharmacokinetic properties of the inhalation agents.

Adult↗
PubMed1994

Isotopomer spectral analysis of cholesterol synthesis: applications in human hepatoma cells.

Cholesterol synthesis from 13C-labeled precursors produces a discrete spectrum of mass isotopomers detectable using gas chromatography-mass spectrometry. The isotopomer spectral analysis (ISA) method matches the observed spectrum of cholesterol isotopomers with a mathematical model to obtain the best fit of model spectrum to data spectrum. The model was based on multinomial probability expressions that simulate cholesterol synthesis as a condensation of mevalonate fragments. As many as four unknown parameters, representing fluxes between compartments, were included in the model. Models were developed to assess cholesterol synthesis from 13C-enriched precursors including mevalonate, acetate, acetoacetate or octanoate. Models were tested in the human hepatoma cell line, Hep G2, which readily incorporated the 13C substrates into cholesterol. The ISA approach was used to estimate the fractional amount of the cholesterol precursors derived from the 13C substrate and the fraction of total cellular cholesterol synthesized in the presence of the 13C substrate. The study demonstrated the feasibility of the ISA approach for a condensation biosynthesis that is not a simple polymerization and for models with more than two unknown parameters.

Acyl Coenzyme A↗
PubMed1989

[Desmoid fibromatosis in absorption infrared spectroscopy, emission spectral analysis and roentgen diffraction recording].

The authors present results of serial quality and quantity microanalyses of bone patterns and dental tissue patterns in patient with desmoid fibromatosis. Methods of absorption spectroscopy, emission spectral analysis and X-ray diffraction analysis with follow-up to x-ray examination are tested. The above mentioned methods function in a on-line system by means of specially adjusted monitor unit which is controlled centrally by the computer processor system. The whole process of measurement is fully automated and the data obtained are recorded processed in the unit data structure classified into index sequence blocks of data. Serial microanalyses offer exact data for the study of structural changes of dental and bone tissues which manifest themselves in order of crystal grid shifts. They prove the fact that microanalyses give new possibilities in detection and interpretation of chemical and structural changes of apatite cell.

Adult↗
PubMed1993

An analytical method for characterizing repetitive motion and postural stress using spectral analysis.

The availability of small, inexpensive electrogoniometers has made wrist posture measurement during repetitive manual work practical. Efficient analytical methods, however, are not currently available for quantifying the degree of repetitiveness and the interaction with postural stress. Spectral analysis was investigated as a method for characterizing repetitive wrist motion and postural stress using a simple peg transfer task. Wrist posture was controlled by adjusting the pegboard location and by having subjects reach over an obstruction. Work pace was externally controlled using an auditory signal. Angular wrist flexion/extension and ulnar/radial deviation was recorded using a 60 Hz sample rate. Power spectra were computed by stratifying data segments into individual work elements, divided by break points associated with the task. Peak spectral magnitudes and frequency components corresponded closely with joint displacement amplitudes and repetition rates. Spectrum DC component magnitudes were directly related to sustained wrist postures.

Cumulative Trauma Disorders↗
PubMed1992

Beta-blocking effect of propafenone based on spectral analysis of heart rate variability.

RR variability was analyzed in 15 patients with ventricular arrhythmias to evaluate whether the antiarrhythmic action of propafenone is associated with alteration of neural control mechanisms. Before drug administration, spectral analysis of RR variability was characterized by 2 major components at low and high frequency, which are considered to reflect sympathetic and parasympathetic modulation of the heart period. After propafenone (600 to 900 mg/day), there was a marked reduction in RR variance (826 +/- 184 to 412 +/- 77 ms2; p < 0.05), although the mean RR interval was unchanged. The drug significantly reduced the low-frequency component (52 +/- 6 to 28 +/- 4 nu) and augmented the high-frequency component (39 +/- 6 to 55 +/- 5 nu). As a result, the low-/high-frequency ratio (an index of sympathovagal balance) decreased from 2.0 +/- 0.4 to 0.6 +/- 0.1. A positive correlation between serum levels and drug-induced changes in the low-frequency component was also observed. Furthermore, the increase in the low-frequency component induced by tilt (53 +/- 5 to 79 +/- 3 nu) was markedly attenuated after drug administration (27 +/- 5 to 54 +/- 7 nu). Thus, propafenone administration is associated with changes in spectral components that are consistent with a beta-blocking effect of the drug.

Adrenergic beta-Antagonists↗
PubMed2004

Spectral analysis of calcium oscillations.

Calcium (Ca2+) oscillations are universal signals exploited by cells to regulate a vast number of cellular processes. Frequency and amplitude, the key features of oscillating waves, can yield information that can be decoded by intracellular processes. Analysis and quantification of Ca2+ oscillations are crucial for understanding the general concept of Ca2+ signaling. This protocol presents a method for performing spectral analysis of Ca2+ oscillations using MATLAB software.

Calcium↗
PubMed1990

Sympathetic activation during treadmill exercise in the conscious dog: assessment with spectral analysis of heart period and systolic pressure variabilities.

We studied in seven conscious dogs the dynamic rearrangements in neural control of heart rate and left ventricular pressure during treadmill exercise as assessed by spectral analysis. The presence, at rest, of a major high-frequency component (HF), an indicator of vagal tone, was reverted during exercise to a major low-frequency component (LF), an indicator of sympathetic activation. These changes were blunted by chronic beta and alpha 1 adrenergic receptor blockade.

Animals↗
PubMedDate not supplied

Relationship between sympathetic skin response and power spectral analysis of heart rate variation in patients with type 2 diabetes.

We measured sympathetic skin response (SSR), a measure of sympathetic sudomotor function, and compared SSR with other quantitative neurological tests including power spectral analysis (PSA) of heart rate variations in 60 type 2 diabetic subjects. SSR was detected in all 20 age-matched healthy subjects but was absent in 17 patients with type 2 diabetes (28%) (P<.01). Even after exclusion of diabetic patients with absent SSR, the SSR amplitude in diabetic patients was significantly lower than in healthy subjects (P<.05). Both the low frequency power of R-R intervals, which reflects both cardiac sympathetic and parasympathetic function, and the postural fall in systolic blood pressure were significantly lower in the diabetic patients with absent SSR than in those with present SSR (P<.05 and.001, respectively). However, we found no significant difference in the high frequency power of R-R intervals, which reflects accurately cardiac parasympathetic function, between the diabetic patients with absent SSR and those with present SSR. In the diabetic patients with present SSR, SSR amplitude was also positively correlated with the postural fall in systolic blood pressure, low-frequency (LF) power, and high-frequency (HF) power. These results suggest that SSR is a useful and sensitive method for evaluating diabetic autonomic neuropathy, and that sympathetic sudomotor neuropathy may be preceded by cardiac parasympathetic neuropathy in patients with type 2 diabetes.

Diabetes Mellitus, Type 2↗
PubMed1988

Spectral analysis of heart rate variability of lizard, Gallotia galloti.

The beat-to-beat heart rate of the lizard, Gallotia galloti, at rest shows short-term oscillations, the frequency of which varies with body temperature. Spectral analysis of the heart rate variability signal shows that, above 20 degrees C, two major frequency components are present: the first component has a mean frequency ranging from 0.032 at 20 degrees C to 0.070 Hz at 35 degrees C and the second from 0.039 at 20 degrees C to 0.10 Hz at 35 degrees C of body temperature. The beat-to-beat heart rate variability does not seem to be correlated with ventilatory activity. The two spectral components could be associated as in mammals with the activity of the control systems that regulate the circulation, especially with the cutaneous vasomotor thermoregulatory and endogenous pressure vasomotor activities. Transient interactions between both components are described.

Animals↗
PubMed1989

Spectral analysis of the central nervous system effects of the relaxation response elicited by autogenic training.

This study examined the effects of the relaxation response, elicited by autogenic training, on central nervous system (CNS) activity. We used computerized spectral analysis of EEG activity as a dependent measure. After baseline EEG data were obtained for all subjects, the experimental group practiced standard autogenic exercises for 15 experimental sessions with home practice. The control subjects received the same number of sessions under identical conditions, except that they listened to a pleasant radio show without home practice. Subjects were then posttested to assess the acute and chronic effects of autogenic training and the relaxation response on CNS activity. The results indicated significant acute effects differences between groups; the experimental group showed greater increases in theta and greater decreases in alpha percent total power. The results suggest that the relaxation response elicited by autogenic training produces significant acute changes in EEG activity and a characteristic spectral pattern; the results also suggest that focusing attention on a repetitive, internal stimulus is a key element in Benson's relaxation response model.

Adolescent↗
PubMed1998

Cross-spectral analysis of physiological tremor and muscle activity. I. Theory and application to unsynchronized electromyogram.

We investigate the relationship between the extensor electromyogram (EMG) and tremor times series in physiological hand tremor by cross-spectral analysis. Special attention is directed to the phase spectrum and the effects of observational noise. We calculate the theoretical phase spectrum for a second-order linear stochastic process and compare the results to measured tremor data recorded from subjects who did not show a synchronized EMG activity in the corresponding extensor muscle. The results show that physiological tremor is well described by the proposed model and that the measured EMG represents a Newtonian force by which the muscle acts on the hand.

Biomechanical Phenomena↗
PubMed1984

All-night spectral analysis of the sleep EEG in untreated depressives and normal controls.

Sleep was recorded in nine drug-free depressive patients and nine age- and sex-matched normal control subjects. All-night spectral analysis of the sleep electroencephalogram (EEG) showed a significantly reduced power density in the 0.25-2.50 Hz band in the depressive group. Power density values integrated over the entire frequency range (0.25-25.0 Hz) exhibited for both groups a decreasing trend over the first three non-REM/REM sleep cycles. In each cycle depressives had lower values than controls. The results are consistent with hypothesis that the build-up of a sleep-dependent process is deficient in the sleep regulation of depressive patients.

Adult↗
PubMed1999

Power spectral analysis of short-term RR interval and arterial blood pressure oscillations in the lizard, Gallotia galloti: effects of sympathetic blockade.

The role of the sympathetic limb of the autonomic nervous system (ANS) in the mediation of oscillations in consecutive beat-to-beat RR interval (RRI) and systolic blood pressure (SBP) values of lizards, Gallotia galloti, was investigated using spectral analysis and measuring effects of autonomic blockers. alpha-Adrenergic blockade decreased the power spectral density (PSD) of both RRI and SBP very low frequency (VLF: 0.007-0.055 Hz) and low frequency (LF: 0.055-0.150 Hz) bands, whereas beta-adrenergic blockade increased the PSD of both RRI- and SBP-VLF and RRI- and SBP-LF bands. These findings suggest that in lizards 1) the VLF and LF peaks of RRI and SBP power spectra are alpha-adrenergic mediated, and that 2) the beta-adrenergic activity of the sympathetic system may act buffering all RRI and SBP oscillations below 0.150 Hz. These results, when analyzed jointly with the ones obtained from a previous study (De Vera and González. 1997. Comp Biochem Physiol 85A:389-394) on the effects of parasympathetic blockade on lizards' RRI and SBP oscillations, demonstrate that these reptiles, like mammals, exhibit spontaneous short-term oscillations in their HR and SBP which are mediated by the ANS. However, unlike mammals, the RRI and ABP low-frequency oscillations in Gallotia seem to be similarly affected by the ANS and appear to be powered by alpha-adrenergic and parasympathetic activities and buffered by beta-adrenergic activity.

Adrenergic alpha-Antagonists↗
PubMed1984

Spectral analysis of biochemical reactions used for identification of bacteria.

To define parameters for optimizing automated discrimination of bacterial biochemical reactions certain theoretical considerations of spectrophotometric analysis were explored. One-hundred and one recent clinical isolates of gram-negative bacilli (21 species) were inoculated into AP1 20 E strips and read manually after 24 hours. With spectrophotometric scanning, the AP1 reactions could be classified into three analytical categories: pH change, production of new products, and darkening of the medium. Whereas single wavelength analysis gave 2.9% disagreement from the visual, multiple wavelength analyses were uniformly more accurate. The best results for pH change reactions were obtained by calculating a ratio of two wavelengths. New color reactions were best interpreted by demonstration of the new peak, whereas darkening reactions required quantitation of the area under the entire curve. With these methods, a 99.3% overall agreement of individual reactions and a 97% agreement of identification were achieved. Multiple-point analysis of spectra coupled with computerized interpretation of the data should help resolve the problem of equivocal reactions in bacterial identification schemes optimized for spectral analysis.

Bacteriological Techniques↗
PubMed2000

Power spectral analysis of heart rate in hypothyroidism.

OBJECTIVE: The aim of the present study was to evaluate the impact of hypothyroidism on the autonomic regulation of the cardiovascular system by analysing separately sympathetic and parasympathetic influences on the heart. DESIGN: In seven newly diagnosed untreated hypothyroid patients we analysed power spectral density of heart rate cyclic variations at rest, while lying, and while standing. The same protocol was repeated after the induction of stable euthyroidism by levothyroxine (L-T(4)) treatment. The results were also compared with those obtained from seven age-, sex- and body mass index-matched control subjects. METHODS: Heart rate variability was evaluated by autoregressive power spectral analysis (PSA). This method allows reliable quantification of low frequency (LF) and high frequency (HF) components of the heart rate power spectral density. These are considered to be under mainly sympathetic and purely parasympathetic control respectively. In addition, heart rate variations during deep breathing, lying to standing, and Valsalva's manoeuvre were assessed. RESULTS: PSA showed a sharp reduction in the HF (parasympathetic) component in hypothyroid subjects compared with controls (lying, 29.4+/-5.4 vs 47.7+/-6.3 normalized units (NU) (means +/- s.e.m.), P<0.05; standing, 14.0+/-3.5 vs 32.1+/-3.6NU, P<0.005). Conversely, the LF (mainly sympathetic) component was higher in hypothyroid subjects than in controls (lying, 61.6+/-6.4 vs 45.4+/-6.7 NU; standing, 71.7+/-8.0 vs 53.1+/-5.6NU), this difference being significant in the standing position. Hence, the LF/HF ratio, which is considered an index of sympathovagal balance, was increased in hypothyroid subjects while both lying (2.75+/-0.6 vs 1.16+/-0.3; P<0.05) and standing (10.0+/-3.7 vs 1.85+/-0.3; P<0. 02). Total heart rate variability, expressed as total power spectral density, was lower in hypothyroid patients than in control subjects, this difference being significant in the lying position (574+/-126 vs 2302+/-994ms(2), P<0.05). In patients re-examined after L-T(4) therapy, complete normalization of cardiovascular parameters was observed (LF/HF ratio, lying, 1.26+/-0.4; standing, 2.56+/-0.8, both P<0.01 vs baseline values). The response to conventional cardiovascular autonomic tests was not significantly different between hypothyroid patients and healthy controls, and did not change in patients after therapy. CONCLUSIONS: These results suggest that, contrary to the clinical picture, thyroid hormone deficiency is associated with an increased sympathetic influence on the autonomic cardiovascular system. The changes in sympathetic function could be explained by a secondary adaptation to an altered cardiovascular responsiveness.

Electrocardiography↗
PubMed2005

EEG spectral analysis and coherence in children with hemiparetic cerebral palsy.

BACKGROUND: Hemiparetic cerebral palsy (HCP) is described as having two main forms: arm-dominant, associated with large cortical/subcortical lesions and leg-dominant, associated with central white matter lesions. MATERIAL/METHODS: Twelve children with HCP underwent clinical assessment and imaging studies. For each child, 20 artifact-free EEG epochs, each of 2s duration, were selected for spectral analysis and coherence functions. The objective of this research was to estimate EEG spectral power, interhemispheric coherence (ICoh), and intrahemispheric (Hcoh) coherence in children with HCP as compared to healthy children. RESULTS: Significant differences between the HCP and control children were detected in the distribution of alpha, theta, delta and beta rhythms over the left and right hemispheres. The ICoh values in the alpha band in the temporal, parietal and occipital regions were significantly lower in the HCP patients than in the controls. There was a significant ICoh increase in the HCP in the theta and delta band, involving frontal and temporal derivations. The significantly lower ICoh values in the HCP children in the beta band involved the frontal, central, parietal and occipital derivations. A higher HCoh value in the HCP children in the alpha band was detected at the right hemisphere. CONCLUSIONS: The lower ICoh at the temporal, parietal and occipital derivations in the alpha band implies hypoconnectivity between the right and left hemispheres. HCoh asymmetry, which implies relative hypoconnectivity within the left hemisphere as compared with the right, suggests that functional hemispheric differentiation may be diminished.

Adolescent↗