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At least 523 records · Page 29Linked to original sources
PubMedDate not supplied

Identification of lipophilic flavones and flavonols by comparative HPLC, TLC and UV spectral analysis.

The identification of lipophilic flavones and flavonols using a combination of high performance liquid chromatography, thin layer chromatography and UV spectral analysis is discussed. Data are provided for the flavones, apigenin, luteolin and tricetin and twelve of their methyl ethers, 8-hydroxyluteolin, 6-hydroxyluteolin and scutellarein and fourteen of their methyl ethers, and some 6,8-dihydroxyapigenin and 6,8-dihydroxyluteolin derivatives. Data for some forty two flavonols with extra 6- and/or 8-hydroxylation, mostly 6-hydroxykaempferol and quercetagetin derivatives, are also presented. The remaining compounds analysed include fourteen 5-deoxyflavones, four 5-methoxyflavones and five 5-deoxyflavonols plus further 5-hydroxylated flavones and flavonols without B-ring oxidation or with 2'-, 5'- or 6'-hydroxylation.

Chromatography, High Pressure Liquid↗
PubMed2004

Spectral analysis of skin laser Doppler blood perfusion signal during cutaneous hyperemia in response to acetylcholine iontophoresis and ischemia in normal subjects.

Spectral analysis of skin laser Doppler (LD) signal was performed using Fourier transformation in twelve healthy subjects in order to compare post-ischemic hyperemia and acetylcholine (ACh) iontophoresis tests for the exploration of cutaneous microcirculatory endothelial function. Within the frequency range studied of 0.009-1.6 Hz, five different frequency intervals were considered, arising from local (endothelial and myogenic) and central (neural, respiratory and cardiac) regulatory mechanisms. The power density (PD) for each of the five frequency intervals considered was measured in perfusion units (PU)/Hz, in each subject, before and in response to ischemia and to ACh iontophoresis, using a dedicated software. The relative contribution of each frequency interval was calculated as per cent rate between each PD and the sum of the PD of the five frequency interval considered. PD of LD signals in response to ischemia and Ach iontophoresis significantly increased for all the five frequency intervals considered. A significant increase (from 25.0+/-6.3 to 48.3+/-17.8; p<0.01) in the relative contribution of 0.009-0.02 frequency interval, referred to endothelium activity, was observed only in response to ACh iontophoresis. No significant increase in the relative power contribution was observed in response to ischemia for any of the five frequency intervals considered. These data suggest that ACh iontophoresis test is more adequate than post-ischemic hyperemia test in exploring the skin microcirculatory endothelial function in normal subjects.

Acetylcholine↗
PubMed1994

Spectral analysis of blood pressure and heart rate variability in response to stress from air-jet in the Lyon rat.

1. Power spectral analysis of the frequency of wave-forms of blood pressure and heart rate was used to characterize short-term fluctuations of these parameters in three strains of conscious Lyon rat, normotensive (LL and LN) and hypertensive LH. 2. A mild stress produced by means of a jet of air elicited blood pressure rises, associated with tachycardia. This response was of similar magnitude in the three strains. The stressor amplified the medium frequency (195-605 mHz) Mayer waves of blood pressure and heart rate which are under autonomic control. 3. Clonidine (10 micrograms kg-1 i.v.) lowered blood pressure and heart rate and dramatically reduced the amplitude of blood pressure and heart rate oscillations in the frequency region of 195-605 mHz. 4. A jet of air applied after clonidine administration led to blood pressure rise associated with tachycardia and enhanced oscillations in the 195-605 mHz region. 5. These results indicate that in Lyon normotensive and hypertensive rats, a mild emotional stressor elicits blood pressure and heart rate rises associated with spectral modifications reflecting sympathetic hyperactivity. Clonidine lowers blood pressure and heart rate and reduces their related variabilities. This effect is more pronounced in LH rats than in their normotensive controls. Clonidine appears to reduce the autonomic response to stress as indicated by the medium frequency oscillations.

Analysis of Variance↗
PubMed1989

Heart rate spectral analysis of fasting-induced bradycardia of cattle.

The autonomic mechanisms of fasting-induced bradycardia of cattle were studied using heart rate spectral analysis. This was performed on digitized, lead II, surface electrocardiograms from conscious, fed, and 48-h-fasted adult cows. Fasting resulted in a significant (P less than 0.05) decrease in resting heart rate and a significant (P = 0.0041) increase in low frequency (0-90 mHz) power spectral area. Administration of atropine sulfate (0.02 mg/kg iv) in either the fed or fasted state resulted in a significant (P less than 0.001) decrease in both low-frequency and high-frequency (100-400 mHz) power spectral areas. Significant (P less than 0.05) increases in serum total bilirubin, inorganic phosphorus, and total protein were associated with fasting. Significant decreases were seen in fasting serum aspartate aminotransferase and potassium values. Manual evacuation of the rumen of seven steers with chronic rumen fistulae resulted in a mean percent decrease in heart rate of 22 +/- 0.9% (mean +/- SE). These results indicate that in normal cattle a decrease in ruminorecticular fill results in a reflex slowing of the heart rate, due predominantly to an increase in parasympathetic tone.

Animals↗
PubMed2004

Heteronuclear selective refocusing 2D NMR experiments for the spectral analysis of enantiomers in chiral oriented solvents.

We report the use of carbon-proton heteronuclear selective refocusing 2D NMR experiments dedicated to the spectral analysis of enantiomers dissolved in weakly ordering chiral liquid crystalline solvents. The method permits the extraction of carbon-proton residual dipolar couplings for each enantiomer from a complex or unresolved proton-coupled 13C spectral patterns. Illustrative examples are analysed and discussed. It is shown that an accurate determination of enantiomeric excess is possible.

Algorithms↗
PubMedDate not supplied

[ECG spectral analysis in quick death, during clinical death, and in the early postresuscitation period].

The article deals with the results of ECG amplitude-frequency analysis conducted in 17 experiments on dogs in the process of quick death, clinical death, and early postresuscitation period. In group 1 (8 animals) circulatory arrest occurred after ventricular fibrillation, in group 2 (9 animals) clinical death was induced by acute blood loss. The ECG was recorded in 3 orthogonal leads after Frank. The spectral analysis was conducted on a Cb-1-ts-02 spectrobiograph. The spectral form coefficient was calculated to study the relationship of the high- and low- frequency components of the spectrum. The total power of the spectrum was evaluated according to the sum value of maximum frequency peaks in 4 fixed ranges. Analysis of changes of the spectral components of the ECG signal showed them to occur in phases in the process of dying and in restoration of vital functions. The use of the method provides for a new quantitative and qualitative evaluation of the ECG.

Animals↗
PubMedDate not supplied

Psychophysiological mechanisms in panic disorder: a correlative analysis of noradrenaline spillover, neuronal noradrenaline reuptake, power spectral analysis of heart rate variability, and psychological variables.

BACKGROUND: The risk of adverse clinical cardiac events is increased in patients with panic disorder (PD). We evaluated possible mechanistic links between PD and heart disease. We estimated cardiac vagal activity from heart rate variability (HRV) measurements and quantified sympathetic nervous system (SNS) activity using plasma noradrenaline tracer kinetics methodology. METHODS: Thirty-nine people with PD and 39 age- and gender-matched healthy volunteers were studied. In 19 participants with PD, both HRV and plasma noradrenaline kinetics were tested; in 20 with PD and 20 healthy volunteers, HRV measurements only were made, whereas in 19 healthy volunteers, noradrenaline kinetics only was tested. All panic disorder participants completed psychological measures of anxiety sensitivity and state and trait anxiety; healthy volunteers in whom HRV was measured also provided psychological measures. RESULTS: Sympathetic nervous tone in the heart, based on rates of cardiac noradrenaline spillover, was normal in PD. Noradrenaline and adrenaline plasma clearance and plasma tritiated noradrenaline and adrenaline extraction in transit through the heart, all dependent on the noradrenaline transporter (NET), were reduced in PD. Psychometric testing linked inhibition of anger to this deficit in NET functioning. Anxiety sensitivity was specifically associated with impaired cardiac NET. High- and low-frequency heart rate spectral power was unrelated to all plasma noradrenaline kinetics measurements. CONCLUSION: Defective neuronal reuptake of noradrenaline, by augmenting the sympathetic neural signal in the heart, might have a dual effect, sensitizing the heart such as to lead to symptom development (and thus perhaps causing panic disorder) and, second, potentially contributing to adverse cardiac events in established PD.

Adult↗
PubMed1996

Assessment of autonomic nerve function in acute intermittent porphyria; a study based on spectral analysis of heart rate variability.

OBJECTIVES: To assess the function of the autonomic nervous system in patients with acute intermittent porphyria by spectral analysis of the heart rate variability. DESIGN: A cross-sectional case-control study. SETTING: Patients were examined at the Primary Health Care Centre, Arjeplog and at Umeå University Hospital, where the controls were also examined. SUBJECTS: Twenty-three patients with acute intermittent porphyria verified by DNA analysis and 92 healthy controls were included. MAIN OUTCOME MEASURES: The mid-frequency band power after tilting was used to evaluate sympathetic function, and the high frequency band power during controlled breathing at 12 breaths min-1 and the mid-frequency band power during controlled deep breathing at 6 breaths min-1 were used to evaluate parasympathetic function. RESULTS: There was no evidence of sympathetic dysfunction in the patients. The mid-frequency band power during controlled deep breathing at 6 breaths min-1 was significantly (P = 0.02) lower in the patient group. CONCLUSIONS: Our findings indicate a parasympathetic dysfunction in patients with acute intermittent porphyria. This may be causally related to sudden cardiac death and the life-threatening arrhythmias which have been observed in this disorder.

Adult↗
PubMed2000

Autonomic nervous function after evening bright light therapy: spectral analysis of heart rate variability.

In order to investigate the effects of 5000 lx evening bright light on autonomic nervous function, a spectral analysis was used to assess heart rate variability in consecutive 5-min epochs just after 60 min of bright light therapy was given to 12 young women (range: 20-21 years of age). The study revealed that a low frequency band (LF) increased in bright light conditions (BL) in comparison with controlled conditions (CL). High frequency band (HF), LF:HF ratio and the coefficient of variance (CV R-R) were not significantly different between the two conditions. These results indicate that 5000 lx evening bright light may affect sympathetic nervous system activity in healthy women.

Adult↗
PubMed1997

Autonomic differences between athletes and nonathletes: spectral analysis approach.

The purpose of this study was to assess the adaptive effects of endurance training on autonomic function in athletes with spectral analysis of cardiovascular variability signals. Continuous ECG, arterial blood pressure (ABP), and respiratory signals were recorded from 15 athletes (VO2max > 55 mL.min-1.kg-1) and 15 nonathletes (VO2max < 45 mL.min-1.kg-1) during 10 min at sitting position. Autonomic function was assessed by low frequency power (LF power: 0.06-0.14 Hz) and high frequency power (HF power: the region of the respiratory frequency based on respiratory spectrum) obtained from the autospectra of RR interval, systolic arterial pressure (SAP), and diastolic arterial pressure (DAP) variability signals. The spontaneous baroreflex sensitivity was evaluated by the moduli, BRSLF and BRSHF, of the transfer function between RR interval and SAP variability in LF and HF bands. The resting HR in athletes was significantly lower than that in nonathletes. The HF power, an index of parasympathetic activity, in RR interval spectra were significantly higher in athletes than in nonathletes. Meanwhile, the LF power (an indicator of sympathetic activities contributing to RR interval and of ABP variabilities) showed no significant difference between both groups, although that of athletes was slightly less than that of nonathletes. Also, BRSLF and BRSHF were not significantly different between athletes and nonathletes. These results indicate that endurance training results in the enhanced vagal activities in athletes, which may contribute in part to the resting bradycardia.

Adult↗
PubMed1997

Spectral analysis applied to hepatobiliary dynamic scintigraphy with 99Tcm-N-pyridoxyl-5-methyltryptophan.

This study was performed to evaluate the application of spectral analysis (SA) to hepatobiliary dynamic scintigraphy with 99Tcm-N-pyridoxyl-5-methyltryptophan (99Tcm-PMT) in 82 patients with a wide range of liver function, and to compare it with compartment analysis (CA) and deconvolution analysis (DA). The rate of uptake of PMT by the liver from the blood (k1) obtained by SA (y, min-1) agreed well with the k1 value obtained using CA (x, min-1) (y = 1.079x + 0.000, r = 0.993, standard error of the estimate (S.E.E.) = 0.042 min-1). The mean residence time (MRT) of PMT in the liver obtained by SA (y, min) also agreed well with the MRT value obtained by DA (x, min) (y = 1.036x - 0.759, r = 0.967, S.E.E.-1.014 min) and that obtained by CA (x, min) (y = 0.859x + 1.006, r = 0.931, S.E.E. = 1.428 min). The fraction of the measured blood activity superimposed on the true liver activity (f) obtained by SA (y) correlated well with the f value obtained by CA (x) (y = 1.168x - 0.004, r = 0.924, S.E.E. = 0.043). We conclude that the application of SA to hepatobiliary dynamic scintigraphy with PMT appears to be useful in evaluating the functional status of the liver, since it facilitates the interpretation of the kinetic behaviour of PMT in the liver and allows us to extract quantitative parameters corresponding to those obtained by CA or DA.

Biliary Tract↗
PubMed2005

[Spectral analysis of the electrical activity of the left colon].

OBJECTIVE: The present study was conducted with the objective of carrying out a spectral analysis of the electrical activity of the left colon. METHODS: Seventeen female patients indicated for complete abdominal hysterectomies were studied. Three pairs of electrodes were implanted in the left colon. After the recuperation of the postoperative ileus, data was collected from the myoelectric activity of the colon from patients who were on an unrestricted diet and were being released from hospital. The signals of the electric activity of the colon were captured and fed into a computer, by means of a data collection system, DATAQ, Akron, OH, Series 200, which identified and captured frequencies between 0,02 and 10 Hz. The data was registered, stored and analysed using the software programme WINDAQ 200, for Windows. The acquisition data produced a sample of 40 points per second. For the electrical analysis, the average voltage of the electrical wave in the three electrodes of all the patients, expressed in millivolts, was considered, together with the maximum and minimum values, the RMS (root-mean-square), the skewness and the results of the Fast Fourier Transforms. RESULTS: 1. The average root-mean-square (RMS) in the left colon was 220,828 millivolts; 2. During a long period of contraction, the RMS was elevated in a statistically significant manner from 94,590 millivolts during a rest period to 487,950 millivolts. CONCLUSIONS: The knowledge of the electrical characteristics of the colon resulting from this study, is one more stage in this line of research, where electromyographic alterations of the colon are studied. The definition and search for an electrical pattern of the colon should be a fundamental step in the clinical handling of physiopathological alterations of the colon.

Adult↗
PubMedDate not supplied

[Spectral analysis of the EEG and intracortical connections in the presence of a pathologic focus at different levels of the human brain].

EEG spectral analysis in 68 patients with focal brain lesions has shown that EEG power spectra are characterized by greatest changes in the focal zone, as manifested in the augmenting of the slow component and diminution of the alpha-component. By means of phasic analysis it has been established that the slow component is generated in the focal zone. Analysis of the complex function of EEG coherence detected different variants of changes in the spatial-temporal organization of cortical electrical activity, determined by localization of the focus and the extent of its impact on the brain. The revealed discordance of EEG connections, diminution of coherence in some parts of the hemispheres with simultaneous enhancement in the others, manifested differently in different physiological rhythms ranges, reflects an impairment in the structure of intracortical connections of electrical processes, which is typical of the normal brain.

Brain Neoplasms↗
PubMedDate not supplied

Spectral analysis of Doppler signal in the prophylaxis of ischemic cerebrovascular accidents in extra- and/or intracranial carotid and vertebral systems.

Using continuous-wave spectral analysis of Doppler signal (SADS) and/or pulsed-wave transcranial Doppler ultrasonography (TCD-US) we examined 263 patients with ischemic cerebrovascular diseases (ICVD) symptoms in the carotid and vertebrobasilar (V-B) systems. The degree of stenosis was established by taking into consideration the parameters of the spectrum of frequency (systolic peak velocity--SV; end-diastolic velocity--DV); the ratio between SV of internal carotid artery (ICA) and common carotid artery (CCA); the ratio between DV of ICA and CCA as well as the value of the spectral broadening (SB) index. The diminution of DV in CCA with increased values of Pourcelot's circulatory resistance index (RP) and spectral broadening index (SB) as compared with the controlateral part, but with apparent increase (over 3.5 kHz) of SV in ICA was constantly observed in significant stenoses of extracranial ICA. Our observations have pointed out that when proximal ICA occlusion is being formed slowly and progressively, ECA (whose increased circulatory resistance under normal conditions reflects diminished diastolic velocities) gradually takes over the hemodynamic characteristics of ICA which is expressed by increased DV, approximating DV and ICA. This situation may give rise to erroneous interpretations.

Blood Flow Velocity↗
PubMed1986

Intraoperative assessment of in situ saphenous vein arterial grafts using pulsed Doppler spectral analysis.

Errors in anastomotic construction, retained competent valves, and arteriovenous fistulas can cause both early and delayed failure of in situ saphenous vein arterial grafts. Pulsed Doppler spectral analysis of midstream flow was compared with arteriography in 50 consecutive in situ saphenous vein bypasses for the detection of unsuspected technical error. Based on spectral changes in the velocity waveform indicating flow disturbance, intact valve cusps could be distinguished from arteriovenous fistulas, and technically unsatisfactory anastomoses were identified. Competent valve cusps were identified in nine (5%) of 180 valve-incision sites, and six anastomoses (6%) were judged unsatisfactory. The presence of severe flow disturbance was always associated with an anatomic defect on arteriography. Incision of missed valve cusps and anastomotic revisions corrected associated flow disturbances. Doppler flow analysis readily located high-flow arteriovenous fistulas, thereby reducing operative time and the need for multiple arteriograms. The high sensitivity of this method (no false-negative assessments) makes it an ideal screening test, resulting in the selective use of operative arteriography.

Angiography↗
PubMed1995

All-night EEG spectral analysis as a tool for the prediction of clinical response to antidepressant treatment.

Earlier investigations have suggested that variables derived from quantified electroencephalographic (EEG) sleep analysis might predict good clinical response in an early phase of antidepressant treatment. In this report we evaluate the predictive value of all-night sleep EEG spectral analysis during the washout period before treatment. We compared the spectral EEG sleep profiles of major depressed inpatients divided into two groups according to an improvement > or = 50% on the Hamilton Rating Scale for Depression. Findings in this population demonstrate the presence of specific characteristics of the responder group compared with the nonresponder group. Delta band relative power was increased in the former group, while theta, alpha, and beta relative power were decreased. All the bands showed decrease in absolute power in the responder group. These results can be interpreted as enhanced sleep intensity in the responder group. All-night sleep EEG spectral variables are valid baseline markers of the functional differences between treatment responders and nonresponders and thus might permit prediction of clinical outcome.

Adult↗
PubMed1998

Real-time spectral analysis of HRV signals: an interactive and user-friendly PC system.

We present a real-time system, built around a PC and a low-cost data acquisition board, for the spectral analysis of the heart rate variability signal. The Windows-like operating environment on which it is based makes the computer program very user-friendly even for non-specialized personnel. The Power Spectral Density is computed through the use of a hybrid method, in which a classical FFT analysis follows an autoregressive finite-extension of data; the stationarity of the sequence is continuously checked. The use of this algorithm gives a high degree of robustness of the spectral estimation. Moreover, always in real time, the FFT of every data block is computed and displayed in order to corroborate the results as well as to allow the user to interactively choose a proper AR model order.

Calibration↗
PubMed1995

Normal sympathetic vasomotor and cardiac parasympathetic activities in patients with primary aldosteronism: assessment by spectral analysis.

The role of the autonomic nervous system in hypertension due to mineralocorticoid excess remains unclear. To address this issue, we performed power spectral analysis of blood pressure (BP) and RR interval oscillations in 20 patients with primary aldosteronism (PA), 54 patients with essential hypertension (EH) and 45 normotensive (NT) subjects. Blood pressure and the degree of organ damage were similar between PA and EH groups. Age did not differ between the three groups. The Mayer wave power spectrum (MWP) of BP (approx. 0.1 Hz), an index of sympathetic vasomotor tone, was smaller in patients with PA than in patients with EH either while subjects were supine (systolic/diastolic; 3.9 +/- 3.2 (SD)/1.5 +/- 1.3 vs. 5.5 +/- 4.2/2.1 +/- 1.6 mmHg2, P < 0.05 for both) or standing (7.6 +/- 6.6/3.0 +/- 3.0 vs. 17.7 +/- 23.7/7.2 +/- 8.3 mmHg2, P < 0.05 for both). Supine respiratory-related power spectrum (RRP) of the RR interval (approx. 0.25 Hz), an index of cardiac parasympathetic tone, was greater in patients with PA than in patients with EH (545 +/- 574 vs. 302 +/- 464 ms2, P < 0.01). The MWP of BP and the RRP of the RR interval were similar between patients with PA and NT subjects. Adrenalectomy reduced the 24-h mean BP (-18 mmHg for systolic BP, P < 0.001; -12 mmHg for diastolic BP, P < 0.01) and increased the 24-h mean heart rate (+8 bpm, P < 0.001). Furthermore, the diastolic MWP increased mildly (+32%, P < 0.05) and the RRP of the RR interval decreased dramatically (-75%, P < 0.01) following adrenalectomy. These results suggest that both vascular sympathetic and cardiac parasympathetic regulatory systems have minor roles in the maintenance of hypertension in patients with PA. The autonomic nervous system contributes more to the maintenance of BP following than prior to adrenalectomy. This information may be useful for the management of hypertension still persists after removal of adrenal adenoma.

Adenoma↗