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Results 501 - 550 of 643
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Bättig K - - 1993
A recently developed device was used in a field study to continuously assess physical activity, heart rate, and cigarette lighting during 2 workdays and 2 days off in 12 female smokers and 12 female non-smokers. Heart rates did not differ between smokers and non-smokers or between workdays and days off; ...
Mukumov M R - - 1992
Static and dynamic chrono-inotropic responses were recorded from both normal and hypertrophic rat auricular myocardium. The slope of the static force-frequency relation for hypertrophic hearts was steeper than that for control hearts. Computer experiments were designed to study the cellular mechanisms underlying the changes in the force-frequency response associated with ...
Kato M - - 1992
The autonomic nervous system is an important neural control system for maintaining cardiovascular stability in humans. Analysis of heart rate variations may provide important clinical information on the influence of anesthesia on the autonomic nervous system and the central nervous system. Therefore, the effects of 1.0, 1.5, and 2.0 minimum ...
Ori Z - - 1992
Experience with frequency domain analysis over the past two decades strongly suggests that it represents a unique, noninvasive tool for achieving a more precise assessment of autonomic function in both the experimental and clinical settings. Available studies indicate that the significance of the HF component is far better understood than ...
Lakie M - - 1992
The cause of essential (low-frequency) tremor is unknown and its relation to physiological (high-frequency) tremor is unclear. We assessed essential tremor in one patient before and after a stereotactic thalamic lesion. The procedure changed the size of the tremor in the right hand but not in the left. Persistence of ...
Aisen M L - - 1992
The tremor of chronic alcoholism, although clinically similar to essential tremor, has been considered a distinct syndrome. Its underlying mechanism was analyzed in five patients (none in the acute stages of alcohol withdrawal) hospitalized in an alcohol detoxification program. All five patients performed tracking tasks in which they pursued a ...
Pizzuti G P - - 1992
It is well known that normal physiological tremor of the fingers and alpha rhythm in the EEG, may share a common frequency band in the region of 10 Hz; that these two characteristics may be in some way related as a function of their frequencies, is a hypothesis which needs ...
Braun R D - - 1992
Oxygen tension was recorded with double-barreled microelectrodes in the retina of anesthetized cats and monkeys. The oxygen tension (PO2) was often observed to undergo spontaneous irregular fluctuations with peak-to-peak amplitudes of about 3 to as much as 20 mm Hg. These fluctuations were observed only in the vascularized inner 40 ...
Wood J C - - 1992
This study employed a new analytical tool, the Binomial joint time-frequency transform, to test the hypothesis that first heart sound frequency rises during the isovolumic contraction period. Cardiac vibrations were recorded from eight open chest dogs using an ultralight accelerometer cemented directly to the epicardium of the anterior left ventricle. ...
Elble R J - - 1992
Step and sinusoidal forcings were delivered to the wrists of 10 patients with advanced essential tremor using a computer-controlled torque motor. Consistent (type 0) phase resetting was produced in only 5 patients, whereas all 10 patients exhibited harmonic and 2:1 subharmonic entrainment of essential tremor. These results indicate that the ...
Winholtz W S - - 1992
Acoustic analysis of vocal tremor has the potential to make significant quantitative and diagnostic contributions to the study of vocal disorders. This paper presents a new device for analysis of vocal tremor. The Vocal Demodulator produces amplitude- and frequency-demodulated outputs and measures the frequency and level (percent) of low-frequency tremor ...
Kunitake T - - 1992
A length of respiratory movement and instantaneous heart rate was divided into 32 segments to adopt computerized power spectrum analysis. An array of frequency spectrum across all the segments was then constructed to demonstrate sequential changes in the respiratory rhythm (0.4 Hz), low (less than 0.1 Hz) and high (0.2-0.4 ...
Gibbs C L - - 1992
The mechanical and energetic consequences of long-term volume-overload (VOL) hypertrophy have been investigated in rabbits and compared with the consequence in sham-operated controls (SOC). Hypertrophy was induced by creating an aortocaval shunt, and the mechanical, biochemical, and energetic properties of the compensated heart were examined approximately 12 wk later. At ...
Kamath M V - - 1992
The power spectrum of heart rate variability contains low frequency (LF = 0.08-0.12 Hz) and high frequency (HF = 0.18-0.30 Hz) components said to represent neurocardiac rhythms. To verify whether such a relationship exists we report a unique study where the heart rate autospectrum was determined in a 28-year-old epileptic ...
Byrne E A - - 1992
Heart rate rhythms have been demonstrated to parallel specific psychological processes. Efficient experimental control of the amplitude of these rhythms would allow evaluation of bidirectional psychophysiological hypotheses. This experiment was performed to examine the specificity of the heart rate rhythm response to oscillatory head-up tilt. Seventy-one adults (36 male, 35 ...
Gonzalez Gonzalez J - - 1992
Acute ingestion of a low dose of alcohol (0.3 g/Kg) in a group of 18 healthy volunteers does not alter RR mean nor RR variance, producing only a slight decrease in the heart rate variability (HRV) measured by the mean momentary arrhythmia. However, power spectral of the HRV signal shows ...
Nollo G - - 1992
The spontaneous beat-to-beat variability of the ventricular repolarization duration was investigated in 21 healthy subjects (age 25-71 years; mean, 40 years) during the basal state in a recumbent position. For each subject, approximately 1,000 consecutive cycles were analyzed with an automated technique. The time series of the RR, QT, and ...
Myers G - - 1992
Heart rate variability (HRV) has become an important noninvasive measure of the integrity of the autonomic nervous system in various disease states. The power spectrum of HRV is a means to separate the instability oscillations of the various feedback mechanisms that contribute to cardiovascular homeostasis. The reliability of HRV data ...
Sakamoto K - - 1992
Physiological tremor, which is the invisible mechanical vibration of body part, was measured for five fingers. It was obtained that the power spectrum always has two peaks at 10 and 25Hz for each of the five fingers. The peaks were considered to be generated in the following two loop systems: ...
Thomsen C - - 1992
Heart motion is a complex combination of translation, rotation, and concentric contraction. Evaluation of these complex motions has been difficult using conventional slice-selective methods. Noninvasive tagging of the heart has been obtained by the use of slice-selective radiofrequency pulses. Through spatial modulation of the magnetization the entire image can be ...
Lin J C - - 1992
The ability non-invasively to detect and monitor the movement of tissues and organs from outside the body provides many worthwhile areas of potential biomedical applications. Several non-invasive microwave techniques for contact and remote sensing of circulatory and respiratory movements and volume changes have been developed. In general, these systems consist ...
Yamamoto Y - - 1991
Heart rate variability (HRV) spectra are typically analyzed for the components related to low- (less than 0.15 Hz) and high- (greater than 0.15 Hz) frequency variations. However, there are very-low-frequency components with periods up to hours in HRV signals, which might smear short-term spectra. We developed a method of spectral ...
Kleiger R E - - 1991
Both time and frequency domain measures of heart rate (HR) variability have been used to assess autonomic tone in a variety of clinical conditions. Few studies in normal subjects have been performed to determine the stability of HR variability over time, or the correlation between and within time and frequency ...
Chapman L J - - 1991
Index finger tremor accompanying voluntary movement was studied in 19 age-matched control subjects and in 19 grain industry employees chronically exposed to carbon disulfide-based fumigants. Visual judgments of tremor amplitude made by neurologists during clinical examinations equaled the sensitivity of computerized tremor amplitude measurements. Tremor frequency variations detectable only with ...
Logigian E - - 1991
In patients with Parkinson's disease and in normal subjects, the influence of tremor on repetitive voluntary movement was investigated in the index finger by comparing frequency of isometric force tremor with frequency of voluntary alternating isometric contractions. Tremor frequency, measured over the range from 0 to 70% maximum voluntary force, ...
Randall D C - - 1991
The purpose of this study was to quantify the relative roles of the canine cardiac parasympathetic and sympathetic nerves in controlling the distribution of power within the heart rate (HR) power spectrum using a highly selective surgical technique to parasympathectomize the SA node. DAta were recorded in awake dogs (n ...
Yamasaki S - - 1991
We studied the responses of sinus cycle length and atrioventricular (AV) nodal conduction to brief, critically timed vagal stimuli in 25 neonatal (9.6 +/- 3.1 days) canines. Vagal stimuli were delivered to the right or left decentralized cervical vagosympathetic trunk as either a single, brief stimulus train or a repetitive, ...
Hayano J - - 1991
The correlations of 11 indexes of heart rate variability were examined with pharmacologically determined cardiac vagal tone in 15 normal subjects at supine rest. After sympathetic influences by intravenous propranolol were eliminated, RR interval variability was measured for 10 minutes under controlled respiration (0.25 Hz), and cardiac vagal tone was ...
Puppi A - - 1991
In CFY rats the tissue redox-state potential (E0') in heart, m. vastus medialis and in the liver, and the heart frequency and QRS amplitudes were measured parallel. It was observed that following compensatory redosis caused by konakion both the autorhythmic heart frequency and QRS amplitudes increased, while after compensatory oxidosis ...
FitzGerald P M - - 1991
Orthostatic tremor is characterized by tremor of the trunk and legs while standing. Rapid frequency has been emphasized as an important criterion for the diagnosis of this tremor. We observed five patients who had the typical findings of orthostatic tremor but had a wide range of frequencies. All five also ...
Celler B G - - 1991
In 12 dogs anesthetised with alpha-chloralose and urethane, and beta-adrenergic blocked with propranolol, the cervical vagi were stimulated for 60 seconds with supramaximal constant current pulses at frequencies between 2.0 and 10 Hz. The time course of the recovery of the cardiac period response, after cessation of vagal stimulation, was ...
Hrushesky W J - - 1991
Multifrequency resonance structure is a basic biological property that confers stability upon oscillating systems. The relationship of the oscillating respiratory and cardiac systems can be characterized by a series of rhythms including the fundamental frequency, the respiratory sinus arrhythmia (Hz 0.12-0.16), slightly lower frequencies 0.04-0.8, as well as very low ...
Hayne H - - 1991
The ontogeny of behavioral and heart-rate orienting responses to a novel olfactory stimulus was examined in three experiments. The results of Experiment 1 demonstrated that behavioral responses to the olfactory stimulus were observed as early as Day 1, although heart-rate deceleration in response to the stimulus was not observed until ...
Láng E - - 1992
The contribution of genetic and environmental control to stress-related cardiovascular reactions was investigated in 10 monozygotic and 10 dizygotic twin pairs during mental arithmetics. Non-invasive indices reflecting vagal and sympathetic activity were used, namely: indices of myocardial contractility based on impedance cardiogram, and spectral components of heart period variance. Autoregressive ...
Chapman L J - - 1990
Tremor was measured from the index finger during low force, position holding in 18 control subjects and 18 battery workers with low level exposure to mercury. All workers were asymptomatic on clinical neurological examination. No differences were found in average tremor amplitudes between the groups, but statistically significant abnormalities in ...
Gresty M - - 1990
Spectral analysis of a tremor record can sometimes produce a spectrum with multiple components of significant amplitude. The problem is to determine whether the presence of several peaks represents the coexistence of separate tremor mechanisms or be a consequence of fluctuations in the frequency or amplitude of a single tremor. ...
Van Galen G P - - 1990
Power spectral density analysis was applied to the frequency content of the acceleration signal of pen movements in line drawing. The relative power in frequency bands between 1 and 32 Hz was measured as a function of motoric and anatomic task demands. Results showed a decrease of power at the ...
Möltner A - - 1990
Autonomic variables have been recommended as measures of the affective-motivational component of the pain response in objective algesimetry. In the present study components of heart rate responses to painful heat stimuli and their relation to stimulus and sensation variables were analyzed. Twelve healthy subjects served. Sixty phasic stimuli of varying ...
Modarreszadeh M - - 1990
We analyzed breath-to-breath inspiratory time (TI), expiratory time (TE), inspiratory volume (VI), and minute ventilation (Vm) from 11 normal subjects during stage 2 sleep. The analysis consisted of 1) fitting first- and second-order autoregressive models (AR1 and AR2) and 2) obtaining the power spectra of the data by fast-Fourier transform. ...
Durand L G - - 1990
A system model based on the simultaneous recording and analysis of the intracardiac and thoracic phonocardiograms to estimate the time-varying properties of the heart/thorax acoustic system of the dog is described. The presence of instrumental noise in the recording of intracardiac phonocardiograms is characterised, and it is demonstrated that its ...
Lombardi F - - 1990
To evaluate if the 0.1-Hz low-frequency oscillations of R-R interval are a reflection of rhythmical pattern of discharge of the sympathetic outflow, we analysed in 10 decerebrate cats heart rate and cardiac sympathetic efferent discharge variability. A predominant low-frequency component was present in both signals, thus suggesting that the 0.1-Hz ...
Gray L - - 1990
The effects of prestimulus activity levels on auditory responsiveness were evaluated in newborn chickens. Rates of peeping were used as measures of prestimulus activity, and delays in the otherwise ongoing vocalizations were used as measures of responsiveness. Results show increased responsiveness to pure tones at intermediate levels of prestimulus activity. ...
Aguirre A - - 1990
Oscillations in RR interval between 0.02 and 1.00 cycles per second (Hz) have been related to the action of the autonomic nervous system. Respiration has been shown to influence RR interval at normal breathing frequencies between approximately 0.16 and 0.5 Hz in children and adults--a phenomenon known as respiratory sinus ...
Hofer E - - 1990
By appropriate placement of two electrodes on the epicardiac surface of Langendorff-perfused hearts, His-bundle and preatrial signals can be recorded by the surface electrogram (S-ECG). These signals are difficult to detect because of their low amplitude of a few microvolts. To improve the monitoring of these low-level potentials we studied ...
Kawahara K - - 1990
Spectral analysis was performed on the heart period fluctuation in vagotomized, paralyzed, and unanesthetized decerebrate cats. The heart period was measured as the time interval between successive R waves of the electrocardiograms. When end-tidal PCO2 was set at the same level as that before immobilization, the power spectral density plot ...
Weiner E - - 1990
The present study was designed to test the existence of behavioral states in the fetus at term using simplified techniques. For this purpose simultaneous recording of the fetal heart activity by means of phonocardiotocography and of fetal body movements by means of real-time ultrasound was performed by using a multichannel ...
Colantuoni A - - 1990
In skin muscle microcirculation of Syrian hamsters, rhythmic diameter changes were studied along the arteriolar network, under normoxic conditions, at rest. A teflon coated-aluminum chamber was implanted in the dorsum skin of animals. The microcirculation was investigated using intravital microscopy technique. Vessel diameters were determined by a computer-assisted method. Power ...
Frank K H - - 1989
The Erlangen micro-lightguide spectrophotometer EMPHO 1 was designed for fast diffuse reflection (remission) spectrophotometry in small tissue volumes. The aim was to construct a compact, modular instrument with a high repetition rate which can be adapted to moving organs, e.g. the beating heart in situ, by the use of highly ...
Furedy J J - - 1989
Small-magnitude (2-3 beats per minute) heart-rate responses can show sex differences if assessed with a psychophysiological approach in which temporally fine-grained methods are used to determine topographical differences. Such differences emerged when 15 males and 37 females were shown videosegments depicting emotional scenes. Specifically, males accelerated to erotic segments (couples ...
Berger R D - - 1989
We present a technique for introducing broad-band respiratory perturbations so that the response characteristics of the autonomic nervous system can be determined noninvasively over a wide range of physiologically relevant frequencies. A subject's respiratory bandwidth was broadened by breathing on cue to a sequence of audible tones spaced by Poisson ...
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