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PubMed2001

Sleep and treatment response in depression: new findings using power spectral analysis.

This study examined quantitative measures of sleep electroencephalogram (EEG) and phasic rapid eye movements (REM) as correlates of remission and recovery in depressed patients. To address correlates of remission, pre-treatment EEG sleep studies were examined in 130 women outpatients with major depressive disorder treated with interpersonal psychotherapy (IPT). To address correlates of recovery, baseline and post-treatment EEG sleep studies were examined in 23 women who recovered with IPT alone and 23 women who recovered with IPT+fluoxetine. Outcomes included EEG power spectra during non-rapid eye movement (NREM) sleep and REM sleep and quantitative REMs. IPT non-remitters had increased phasic REM compared with remitters, but no significant differences in EEG power spectra. IPT+fluoxetine recoverers, but not IPT recoverers, showed increases in phasic REM and REM percentage from baseline to recovery. In NREM sleep, the IPT+fluoxetine group showed a decrease in alpha power from baseline to recovery, while the IPT group showed a slight increase. The number of REMs was a more robust correlate of remission and recovery than modeled quantitative EEG spectra during NREM or REM sleep. Quantitative REMs may provide a more direct measure of brainstem function and dysfunction during REM sleep than quantitative sleep EEG measures.

Arousal↗
PubMed2000

Observer variations in short period spectral analysis of heart rate variability.

25% of the corresponding mean LF/HF ratio. The smallest interobserver variations were found for the 'fixed frequency' method. The data showed that it is advantageous to select the 3-min ECG periods but not to select the frequency regions. Selection of the latter led to an increase in interobserver variation. The results of this study give a realistic impression of the intrasubject and interobserver variation to be expected when measuring the LF/HF ratio. This variation is considerable.

Analysis of Variance↗
PubMed1997

Spectral analysis of intercycle heart fluctuations in Xenopus laevis, conscious or spinalized, treated with calcium channel blockers. Part I.

1. In this study, electrocardiographic second lead tracings were recorded and analyzed online and offline in the conscious and spinalized Xenopus laevis under control conditions and after treatment with at least two effective doses of racemic diltiazem, nifedipine and racemic verapamil hydrochlorides. 2. Heart rates (HR) and intercycle heart rate power spectra (IHRPS) were calculated in the various experimental conditions. 3. Dose-dependent bradycardia was found in most cases, which was associated with dose-related increases in the overall dynamic range of the largest peak of HR variability (increased IHRPS), this being particularly marked at the higher nifedipine dose. The frequency position of the largest peak was unchanged in the spinalized preparation, as well as in the various treatments. 4. These findings may contribute toward a more complete pharmacodynamic definition of calcium channel blockers in their current therapeutic use.

Animals↗
PubMed2000

Synthesis of 2,3- and 3,4-methylenedioxyphenylalkylamines and their regioisomeric differentiation by mass spectral analysis using GC-MS-MS.

3,4-methylenedioxyamphetamine (MDA) derivatives are increasingly abused central nervous system stimulants with neurotoxic properties. In recent years a number of controlled substance analogs (designer drugs) with high structural variety reached the illegal market making their identification an arduous task. The underivatized compounds give very similar or even virtually identical electron impact mass spectra containing mainly intense C(n)H(2n+2)N(+) immonium ions. Using tandem mass spectrometry (MS-MS) the additional structural information contained in the collision induced dissoziation (CID) mass spectra of molecular ions using electron impact (EI) and especially chemical ionization (CI) allowed an unequivocal differentiation of 18 studied regioisomeric 1-(methylenedioxyphenyl)-2-propanamines and 1-(methylenedioxyphenyl)-2-butanamines. Further synthetic methods are presented for 1-(3,4-methylenedioxyphenyl)-N-propyl-2-butanamine, N-isopropyl-1-(3,4-methylenedioxyphenyl)-2-butanamine and four 1-(2, 3-methylenedioxyphenyl)-2-butanamines. N-alkylated 1-(3, 4-methylenedioxyphenyl)-2-butanamine compounds (e.g. MBDB) are also known to be abused psychoactive agents (entactogenes) without the sympatomimetic effects of the 3,4-methylenedioxyamphetamines.

3,4-Methylenedioxyamphetamine↗
PubMed1998

Nuclear magnetic resonance spectral analysis and conformational properties of 11-benzoyl-9,9a,10,11-tetrahydro-4H-indolo[4,3-ab]carbazole.

The structure of 11-benzoyl-9,9a,10,11-tetrahydro-4H-indolo [4,3-ab] carbazole, a candidate molecule to possess significant antitumor or antimicrobial activity, was elucidated using a combination of one-dimensional and two-dimensional nuclear magnetic resonance (NMR) techniques. Its conformational properties were studied using a combination of two-dimensional NOESY spectroscopy and molecular modeling. Such information will be of aid to synthetic chemists who aim to develop derivatives of this structure. It may also provide information about the stereoelectronic requirements that govern their activities.

Anti-Infective Agents↗
PubMed2003

Inverse methods in two-dimensional NMR spectral analysis.

Solid-state NMR is a valuable technique for the study of disordered materials. Analysis of such spectra usually involves solution of so-called ill-posed inverse problems. Here we present a strategy for the analysis of two-parameter two-dimensional NMR problems and test it on 2D DECODER and DOQSY experiments. Using Monte Carlo tests, constraints are determined for the resolution and accuracy of the analysis for both experiments. The methods are finally applied to spectra of spider dragline silk, a heterogeneous solid fibrous protein.

Animals↗
PubMed2003

A comparison of the wavelet and short-time fourier transforms for Doppler spectral analysis.

Doppler spectrum analysis provides a non-invasive means to measure blood flow velocity and to diagnose arterial occlusive disease. The time-frequency representation of the Doppler blood flow signal is normally computed by using the short-time Fourier transform (STFT). This transform requires stationarity of the signal during a finite time interval, and thus imposes some constraints on the representation estimate. In addition, the STFT has a fixed time-frequency window, making it inaccurate to analyze signals having relatively wide bandwidths that change rapidly with time. In the present study, wavelet transform (WT), having a flexible time-frequency window, was used to investigate its advantages and limitations for the analysis of the Doppler blood flow signal. Representations computed using the WT with a modified Morlet wavelet were investigated and compared with the theoretical representation and those computed using the STFT with a Gaussian window. The time and frequency resolutions of these two approaches were compared. Three indices, the normalized root-mean-squared errors of the minimum, the maximum and the mean frequency waveforms, were used to evaluate the performance of the WT. Results showed that the WT can not only be used as an alternative signal processing tool to the STFT for Doppler blood flow signals, but can also generate a time-frequency representation with better resolution than the STFT. In addition, the WT method can provide both satisfactory mean frequencies and maximum frequencies. This technique is expected to be useful for the analysis of Doppler blood flow signals to quantify arterial stenoses.

Algorithms↗
PubMed2003

Quantitative spectral analysis of EEG in psychiatry revisited: drawing signs out of numbers in a clinical setting.

OBJECTIVE: To evaluate the incidence, sensitivity and specificity of abnormal quantitative EEG (QEEG) measures in normal subjects and patients with mental disorders. METHODS: Normalized QEEG measures were blindly assessed in 67 normal human beings and 340 psychiatric patients. QEEG results were correlated to subject condition or diagnosis and magnetic resonance imaging (MRI) findings. RESULTS: QEEG was abnormal in 83% of patients, and 12% of normal subjects. The most frequent abnormality was a decrease in slow (delta and/or theta) bands, either alone, with beta increase, or with alpha decrease, followed by increase in beta band. No normal subject showed delta and/or theta decrease. Slow band decrease was more frequent in depression and mental disorders due to general medical condition, alcohol and drug dependence. However, no pattern was specific of any entity, and patients within the same diagnostic may present different patterns. Delta-theta decrease was correlated with cortical atrophy as seen in MRI. Beta increase was correlated with psychoactive medication. No association was found between any other QEEG pattern and MRI abnormalities, or medication. CONCLUSIONS: Decrease in the delta and theta bands of the QEEG can be regarded as a specific sign of brain dysfunction, and is correlated with cortical atrophy. However, this sign, as other QEEG abnormal patterns, can be found in many different disorders and none of them can be considered as pathognomonic of any specific disorder. SIGNIFICANCE: This work attempted to circumvent the alleged lack of Class I evidence of QEEG utility in the study of psychiatric patients by means of a prospective, blinded study, searching for specific signs of physiopathology in individual patients.

Adolescent↗
PubMed2002

Autonomic imbalance during the day in patients with inflammatory bowel disease in remission. Evidence from spectral analysis of heart rate variability over 24 hours.

BACKGROUND: Autonomic function in inflammatory bowel disease has not yet been studied by means of analysis of 24-hour heart rate variability. AIM: To measure heart rate variability in inflammatory bowel disease patients in remission. PATIENTS AND METHODS: Study population comprised 27 patients with inflammatory bowel disease in remission and 28 healthy, sex- and age-matched controls. Two frequency ranges were analysed: low frequency (0.06-0.15 Hz) and high frequency (0.15-0.40 Hz). RESULTS: Mean values of low frequency and low frequency/high frequency ratio were lower in patients than in controls (p < 0.001). High frequency in patients tended to be higher than in controls (p = 0.09). The only factor that had a marginal effect on heart rate variability indexes was age. In high frequency, there was a significant time effect (p = 0.001) for both groups. There was also a significant time effect in low frequency/high frequency ratio in both groups (p < 0.001). During daytime, the mean values in low frequency/high frequency ratio were lower in patients than in controls (p < 0.001). CONCLUSIONS: There is a shift in the autonomic balance in patients with inflammatory bowel disease in remission towards a condition of relative parasympathetic predominance, which, in the first place, reflects a sympathetic pullback. This imbalance has a circadian rhythm and it is more pronounced during the day.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMedDate not supplied

The maintained discharge of neurons in the cat lateral geniculate nucleus: spectral analysis and computational modeling.

The maintained discharge of neurons along the early visual pathway in mammals constitutes the "noise" from which the visual signal must be discriminated. The statistics of this background noise in cat retinal ganglion cells (RGCs) have been shown to conform to that of a gamma-distributed renewal process (Kuffler et al., 1957; Barlow & Levick, 1969), and power spectrum analysis reveals that this property allows for low noise levels at the temporal-frequency range (0-10 Hz) most important for visual performance (Troy & Robson, 1992). In this study, we compare the statistics of the maintained discharge of cat lateral geniculate neurons with those of its RGC input by simultaneous recordings of spikes and S-potentials in single relay cells of the cat lateral geniculate nucleus (LGN). We demonstrate that, during primarily tonic spiking activity, the LGN maintained discharge preserves the renewal process statistics of its RGC input and also generates relatively little noise at the temporal frequencies important for vision. However, during burst spiking activity, the renewal process model breaks down and increased noise is generated at 2-10 Hz. This suggests that optimization of the visual signal/noise ratio is not a prime consideration in the behavioral states associated with bursting activity in the LGN. The occurrence of burst spikes in LGN relay cells is dependent on the activity of T-type calcium channels in their plasma membranes (Jahnsen & Llinas, 1984a,b). We show that a computational model of LGN relay cells that incorporates T-channel kinetics (Mukherjee & Kaplan, 1995) can correctly simulate LGN maintained discharge statistics during both tonic and bursty firing conditions, and indicates an essential role for this ion channel in determining the dynamic noise properties of the LGN. We also use the computational model to predict how the burstiness of the LGN maintained discharge is affected by the statistics of its RGC input.

Action Potentials↗
PubMed2005

Mass spectral analysis of chloropicrin under negative ion chemical ionization conditions.

A chemical ionization (CI) method is developed for the first time to obtain molecular weight information for chloropicrin (CP), which is used as a chemical warfare agent and as an insecticide. The study includes a detailed investigation on the behavior of CP under electron impact (EI) and CI. Reagent gases of different nature, i.e., methane, isobutane, ammonia, hydrogen, and carbon dioxide, were used for CI analysis. Negative ion mode is found more sensitive than positive ion mode for the EI/CI mass spectrometric analysis of CP, but none of the methods provided molecular weight information, except negative ion CI using ammonia as the reagent gas (NICI (NH3)). The NICI (NH3) showed formation of the quasi-molecular ion, [M + H]-, in addition to other adduct ions. The [M + H]- abundance critically depends on the source temperature, reagent gas pressure, and concentration of the analyte, and it can be 13% under optimized conditions by which CP can be confirmed unambiguously. This method meets the criteria used in official proficiency tests conducted by OPCW for confirming the molecular weight of the unknowns.

Chemical Warfare Agents↗