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At least 955 records · Page 53Linked to original sources
PubMed1997

[A method of fluorescence spectral analysis of lymphocyte function in cancer patients].

A luminescence microspectral examination of lymphocytes in peripheral blood sampled from ovarian tumor patients has shown spectral pattern, and, particularly, parameter alpha (ratio of one-spiral to two-spiral nucleic acids in cell) and parameter alpha distribution pattern to vary in the course of treatment: as efficacy increases, the lymphocyte fluorescence spectrum shows two peaks (lambda = 530 and 640 nm) of nearly identical intensity, parameter alpha grows, too, and its distribution shifts to the right. This mirrors an activation of synthetic and functional processes going on in peripheral blood lymphocytes of patients and points to enhanced non-specific resistance.

Female↗
PubMed1977

[Gas-chromatographic-mass-spectral analysis of aroma-compounds of bread (author's transl)].

Analysis of aroma compounds of whithe bread by means of a combined gas-chromatographic-mass-spectral method was carried out. 29 organic compounds were identified, 20 of which were reported for the first time in bread aroma. These for the first time reported compounds are: 1, 1-diethoxyisopentane, 2-phenylethylformiate, n-butylformate, 2-isooctenal, 2-octenone-4, sec. nonanol, nonanol-1, 2-nonanone-4, 2-decenone-4, 2-decenone-5, 1-dodecenone-3, 2-dodecenone-4, 2-dodecenone-5, dodecanol, octylacetate, ethylbenzoate, nitrobenzene, pentadecanone-2, heptadecanone-2, tridecadience.

Alcohols↗
PubMed1988

The use of alkoxycarbonyl derivatives for the mass spectral analysis of drug-thioether metabolites. Studies with the cysteine, mercapturic acid and glutathione conjugates of acetaminophen.

Alkoxycarbonyl derivatives of the cysteine-, N-acetylcysteine- and glutathione conjugates of acetaminophen have been prepared in aqueous buffer solutions and their chromatographic and mass spectrometric properties examined. Structurally informative fragmentation patterns of the cysteine- and N-acetylcysteine derivatives were obtained when their methyl esters were subjected to analysis by direct insertion chemical ionization (CH4) mass spectrometry, although field desorption and liquid secondary ion mass spectrometric techniques were required in order to obtain satisfactory spectral data for derivatives of the glutathione adduct. Treatment of ethoxycarbonyl derivatives of the three acetaminophen metabolites with N-methyltrifluoroacetamide-based silylating reagents led to the formation of a common volatile product which was ideally suited to analysis by gas chromatography/electron impact mass spectrometry. A mechanism is proposed for the formation of this novel derivative, which appears to possess a benzo-1,3-thioxalane structure, and its mass spectral characteristics are reported. Finally, the utility of alkoxycarbonyl derivatives for the analysis of drug-thioether conjugates in biological fluids is discussed in terms of their advantages for aqueous phase derivatization, purification by high-performance liquid chromatography and characterization by mass spectrometry.

Acetaminophen↗
PubMed2004

Factors influencing heart rate variability power spectral analysis during controlled breathing in patients with chronic heart failure or hypertension and in healthy normotensive subjects.

A decreased LFP (low-frequency power) spectral component of HRV [HR (heart rate) variability] is a risk factor for sudden death in patients with CHF (chronic heart failure). In the present study, we evaluated factors (age, arterial pressures and HR) influencing LFP and HFP (high-frequency power) components in short-term recordings during controlled breathing in patients with CHF or hypertension, and healthy normotensive subjects. In patients with CHF, we also compared LFP values with known markers of sudden death [NYHA (New York Heart Association) class, HR and ejection fraction]. All HRV measures were significantly lower in patients with CHF than in hypertensive and normotensive subjects (P<0.001), and in hypertensive than in normotensive subjects (P<0.05). Stepwise multiple regression analysis showed that, in patients with CHF, LFP was inversely associated with NYHA class (beta=-0.5, P<0.0001) and HR (beta=-0.2, P=0.001) and was positively associated with ejection fraction (beta=0.28, P<0.0001). In patients with CHF, LFP remained unchanged with age. In normotensive and hypertensive subjects, HFP decreased with age, but in patients with CHF it did not. In the >/=60<70 and >/=70 years of age subgroups, we found no difference between HFP in the three groups studied. Hence, in normotensives and hypertensives, LFP tended to diminish with age (beta=-0.4, P<0.0001 in normotensives; beta=-0.4, P<0.001 in hypertensives) and was inversely associated with HR (beta=-0.2, P=0.002 in normotensives; beta=-0.3, P=0.002 in hypertensives). Conversely, in patients with CHF, LFP is predominantly influenced by NYHA class, HR and ejection fraction, but not by age. LFP might therefore increase the sensitivity of factors already used in stratifying the risk of sudden death in patients with CHF.

Adult↗
PubMed2004

Absorption and scattering imaging of tissue with steady-state second-differential spectral-analysis tomography.

A novel approach to reconstructing both the absorption and the scattering properties of a turbid medium simultaneously from steady-state broadband spectral measurements is presented that utilizes second-differential fitting to the water spectrum to estimate the optical path length in tissue. Theoretical and experimental evidence is provided to demonstrate the robust accuracy of the spectroscopy approach and reconstructed absorption images. The steady-state broadband CCD system has the potential to provide accurate chromophore imaging without the technological complexity of time- or frequency-domain systems.

Absorption↗
PubMed1992

Determination of yohimbine and its two hydroxylated metabolites in humans by high-performance liquid chromatography and mass spectral analysis.

The existence of at least two metabolites of yohimbine (YO) in humans is demonstrated. Combined high-performance liquid chromatographic (HPLC), NMR and mass spectral analyses permitted them to be identified as hydroxylated metabolites at the C-10 and C-11 positions. A normal-phase HPLC method allowing the simultaneous determination of YO and its main metabolite, 11-hydroxyyohimbine (11-OHYO), in biological samples is described. This assay was performed using a LiChrosorb Si 60 column and a mobile phase consisting of 0.02 M sodium acetate (pH 5)-methanol (5:95, v/v) at a flow-rate of 1 ml/min. Detection was achieved by a fluorimetric method (excitation at 280 nm and emission at 320 nm). The extraction yields of YO, 10-OHYO and 11-OHYO from plasma were 91.8, 45.3 and 17.8%, respectively, and their respective within-day reproducibilities were 3.8, 1.4 and 5.9%. The between-day reproducibility for YO at the concentrations of 1 and 10 ng/ml were 8.9 and 6.4%, respectively. The accuracy of the method for YO at concentrations of 1 and 10 ng/ml were 5.1 and 2.3%, respectively. The limits of determination of YO, 10-OHYO and 11-OHYO were 0.1, 0.5 and 1 ng/ml, respectively. The method was used in bioavailability study of YO following oral and intravenous administration in humans.

Biological Availability↗
PubMed2002

RADARS, a bioinformatics solution that automates proteome mass spectral analysis, optimises protein identification, and archives data in a relational database.

RADARS, a rapid, automated, data archiving and retrieval software system for high-throughput proteomic mass spectral data processing and storage, is described. The majority of mass spectrometer data files are compatible with RADARS, for consistent processing. The system automatically takes unprocessed data files, identifies proteins via in silico database searching, then stores the processed data and search results in a relational database suitable for customized reporting. The system is robust, used in 24/7 operation, accessible to multiple users of an intranet through a web browser, may be monitored by Virtual Private Network, and is secure. RADARS is scalable for use on one or many computers, and is suited to multiple processor systems. It can incorporate any local database in FASTA format, and can search protein and DNA databases online. A key feature is a suite of visualisation tools (many available gratis), allowing facile manipulation of spectra, by hand annotation, reanalysis, and access to all procedures. We also described the use of Sonar MS/MS, a novel, rapid search engine requiring 40 MB RAM per process for searches against a genomic or EST database translated in all six reading frames. RADARS reduces the cost of analysis by its efficient algorithms: Sonar MS/MS can identifiy proteins without accurate knowledge of the parent ion mass and without protein tags. Statistical scoring methods provide close-to-expert accuracy and brings robust data analysis to the non-expert user.

Amino Acid Sequence↗
PubMed1980

Spectral analysis of allophycocyanin I, II, III and B from Nostoc sp. phycobilisomes.

Low temperature (-196C) and room temperature (25C) absorption spectra of a family of allophycocyanin spectral forms isolated from Nostoc sp. phycobilisomes as well as of the phycobilisomes themselves have been analyzed by Gaussian curve-fitting. Allophycocyanin I and B share long wavelength components at 668 and 679 nm, bands that are absent from allophycocyanin II and III. These long wavelength absorption components are apparently responsible for the 20 nm difference between the 680 nm fluorescence emission maximum of allophycocyanin I and B and the 660 nm maximum of II and III. This indicates that allophycocyanin I and B are the final acceptors of excitation energy in the phycobilisome and the excitation energy transfer bridge linking the phycobilisome with the chlorophyll-containing thylakoid membranes. These Gaussian components are also found in resolved spectra of phycobilisomes, are arguing against this family of allophycocyanin molecules being artifactual products of protein purification procedures.

Cyanobacteria↗
PubMed1992

Spectral analysis of sympathetic discharge, R-R interval and systolic arterial pressure in decerebrate cats.

In 19 decerebrate and artificially ventilated cats, we analyzed, with a power spectral methodology, the variability simultaneously present in R-R interval and in thoracic preganglionic sympathetic outflow. R-R interval was characterized, as already described in humans and other experimental preparations, by two rhythmic components occurring at a frequency of about 0.1 Hz (low-frequency, LF) and at one corresponding to respiratory rate (high-frequency, HF) which, in these experiments, was set at 0.32 Hz. Two similar rhythmic components were also present in the sympathetic discharge. Arterial pressure changes were produced by aorta or vena cava flow obstruction in order to produce reflex responses in sympathetic activity. Reflex sympathetic excitations induced an increase in the LF component of both R-R interval and sympathetic discharge variabilities, while the HF components were simultaneously reduced. In contrast, reflex sympathetic inhibitions were accompanied by a decrease in LF components of both variability signals, while the HF components were simultaneously increased. A significant and positive correlation was found between changes in impulse activity and the amplitude of LF component of either R-R interval or sympathetic discharge variabilities. These data support the hypothesis that the low-frequency component of R-R variability can be used as a marker of sympathetic modulation.

Animals↗
PubMed2003

Spectral analysis of muscle sympathetic nerve activity in heat-stressed humans.

Whole body heating increases muscle sympathetic nerve activity (MSNA); however, the effect of heat stress on spectral characteristics of MSNA is unknown. Such information may provide insight into mechanisms of heat stress-induced MSNA activation. The purpose of the present study was to test the hypothesis that heat stress-induced changes in systolic blood pressure variability parallel changes in MSNA variability. In 13 healthy subjects, MSNA, electrocardiogram, arterial blood pressure (via Finapres), and respiratory activity were recorded under both normothermic and heat stress conditions. Spectral characteristics of integrated MSNA, R-R interval, systolic blood pressure, and respiratory excursions were assessed in the low (LF; 0.03-0.15 Hz) and high (HF; 0.15-0.45 Hz) frequency components. Whole body heating significantly increased skin and core body temperature, MSNA burst rate, and heart rate, but not mean arterial blood pressure. Systolic blood pressure and R-R interval variability were significantly reduced in both the LF and HF ranges. Compared with normothermic conditions, heat stress significantly increased the HF component of MSNA, while the LF component of MSNA was not altered. Thus the LF-to-HF ratio of MSNA oscillatory components was significantly reduced. These data indicate that the spectral characteristics of MSNA are altered by whole body heating; however, heat stress-induced changes in MSNA do not parallel changes in systolic blood pressure variability. Moreover, the reduction in LF component of systolic blood pressure during heat stress is unlikely related to spectral changes in MSNA.

Adult↗
PubMed1994

Spectral analysis of laser Doppler signals in real time using digital processing.

A versatile spectrum analyser was developed to generate and display laser Doppler shift signals, and derived parameters, continuously in real time using a digital signal processing chip. A major attraction of the system is that it is entirely programmable, so that both the algorithms and the attributes of the system, such as window function and frame overlap, can be easily altered. It was used to investigate the relative merits of a variety of algorithms using a blood-flow phantom. An index based on the first moment of the Doppler power spectrum was found to be the most reliable flow indicator, with linearity extending towards a velocity of 5 mm s-1 for a blood haematocrit of 5%. The system is not limited to analysis based on the fast Fourier transform (FFT), and is suitable for non-linear techniques such as maximum entropy spectral estimation (MESE).

Algorithms↗
PubMed1995

[Spectral analysis of body surface ECG maps].

A signal-averaging technique was applied to 60-lead epicardial mapping in dogs and 87-lead body surface mapping in patients with anterior myocardial infarction. By means of fast Fourier transform and inverse fast Fourier transform analysis, we obtained the reconstructed signals of several frequency ranges in the QRS complex. We showed the effects of myocardial infarction on QRS spectral changes and discussed the usefulness of this method for evaluating ventricular tachycardia and left ventricular function after myocardial infarction.

Animals↗
PubMed1995

Spectral analysis of EEG from families.

Electroencephalographic (EEG) activity was obtained under eyes open and eyes closed conditions from ten families, each consisting of a biologically related father, mother and two children. Spectral power (microV2) and mean frequency (Hz) measures from the delta, theta, alpha-1, alpha-2, beta-1, and beta-2 bands were computed for each family member. Non-family controls were constructed from the real family data by randomly pairing non-related individuals with one another, and correlations between the analogous individuals were also computed. The correlations for spectral power between family groups were greater than those obtained from the non-families for theta, alpha, and beta band power. The correlations for mean frequency between family members were greater than those of the non-families for the delta, theta, and alpha bands, although these were not as robust as the spectral power findings. In general, few family membership effects were found for the eyes open/closed or electrode site conditions. The results support findings from twin studies that suggest EEG characteristics are determined at least in part by genetic factors.

Adolescent↗
PubMed2000

Mass-spectral analysis of human interferon-gamma and chloramphenicol acetyltransferase I produced in two Escherichia coli strains.

Recombinant human interferon-gamma and chloramphenicol acetyltransferase I were isolated from two Escherichia coli strains, E. coli LE329 and E. coli XL1-blue and characterized by electrospray ionization mass spectrometry (ESI-MS). The ESI-MS analysis showed higher masses in comparison with the theoretically calculated for both proteins as well as unexpected molecular heterogeneity. The ESI-MS spectral patterns of the proteins depended on the host strain used and were more heterogenous for the proteins isolated from E. coli LE392. One of the proteins (human interferon-gamma obtained from E. coli XL1-blue) was further subjected to BrCN cleavage. The ESI-MS analysis of the polypeptide mixture revealed shift in the molecular mass for two peptides including the last 26 amino acids of the human interferon-gamma molecule.

Biotechnology↗
PubMed1978

Spectral analysis of high resolution direct-derivative melting curves of DNA for instantaneous and total base composition.

Derivative melting profiles of DNA have been obtained directly by recording the difference in absorbance between two identical solutions maintained at a small constant temperature differential. This deltaA is monitored continuously with increasing temperature in a ratio recording spectrophotometer. Resolution of complex hyperfine structure in the profiles of small homogeneous viral DNAs appears to be significantly better than has been produced by various numerical methods of differentiation. In addition, a spectral method has been modified that permits easy analysis for DNA base composition from the ratio of derivative melting curves obtained at 282 and 260 nm. Eight bacterial and three vertebrate DNAs have been analyzed for total base composition from the product of the instantaneous base composition at small temperature intervals (0.05 degrees C) throughout the entire melting region and the integrated area of the 282 nm profile. The results are in excellent agreement with values determined by traditional methods.

Bacillus subtilis↗
PubMed1990

Spectral analysis of heart rate variability signal and respiration in diabetic subjects.

The paper deals with methods of processing ECG and respiration signals which aim at detecting parameters whose values may be correlated to normal and diabetic subjects with or without cardiovascular autonomic neuropathy (CAN). Beat-to-beat R-R duration values of the ECG and discrete series of respiration are obtained from original signals using a recognition algorithm. Power spectrum analysis (autospectra, cross-spectra and coherence via autoregressive modelling) is carried out on segments of about 200 consecutive cardiac cycles. Spectral parameters of the R-R variability signal are obtained as follows: total power, powers of low-frequency (LF) and high-frequency (HF) components, power of the signal which is (or is not) coherent with respiration, in absolute or in percentage values. The experimental protocol considers 40 diabetic patients (21 of whom have diabetic neuropathy) and 14 normals in three different conditions: resting, standing and controlled respiration. The developed spectral parameters seem sensitive enough to differentiate between normal and pathological subjects. These parameters may constitute a quantitative means to be added to the classical diabetic tests for the diagnosis of cardiovascular autonomic neuropathy.

Adult↗
PubMed1987

Myoelectric spectral analysis and strategies for quantifying trunk muscular fatigue.

Objective techniques for assessing trunk musculature with respect to fatigue-related characteristics do not exist. Based on work that relates frequency spectral shift in myoelectric signals to muscular fatigue at other body sites, a study was carried out to investigate and evaluate strategies for application of these techniques to the lumbar musculature. Through evolution of test administration procedures to reduce test time and discomfort as well as data interpretation methods to account for interindividual variability observed in data, an approach was developed for objective measurement of fatigue rate. While abdominal and lumbar muscle groups were assessed in 40 healthy subjects with results presented for 50% and 100% maximum voluntary contraction load levels, the methodology is discussed with emphasis on erector spinae results. The approach involves a normal function fatigue plot. The plot relates fatigue rate as measured by myoelectric spectral characteristics to muscle load normalized by body weight and is independent of the maximum voluntary contraction concept. This relationship forms the basis of comparison of the measured fatigue rate for a subject with questionable function to expected normal values determined from the plot, given the measured load level.

Adult↗
PubMed2005

Mass spectral analysis of synthones of nerve agents for verification of the Chemical Weapons Convention.

This communication describes the synthesis and gas chromatography/mass spectrometric (GC/MS) analysis of N,N-dialkylphosphoramidic dihalides and alkylphosphonic difluorides, which are synthones of nerve agents. The study was undertaken with a view to developing a spectral database of these compounds for verification purposes of the Chemical Weapons Convention (CWC). The modified synthetic approach reported here has advantages over traditional syntheses in terms of time and yield. GC/MS analysis of these synthones yielded electron ionization (EI) mass spectra and, based on these spectra, generalized fragmentation routes are proposed that rationalize most of the characteristic ions.

Amides↗