Steroyl phosphonates. 3. Dimethyl phosphonates in the estrone series.
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Androstanes↗
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Evidence on the local character of spatial frequency channels in the human visual system.
The question has been raised as to whether there exists any transfer of information between neighboring retinal areas following presentation of spatially limited optical stimuli. Our experiments were aimed at mechanisms by which spatial frequency information could be transferred from one part of the visual field to another. Within a 0.9 degree X 2.5 degree section of the 3.6 degree X 2.5 degree testfield the observers adapt to a number of moving sinusoidally-modulated brightness or hue gratings of different spatial frequencies. As known by many publications the sensitivity to spatial frequencies changes in the adapted area. We find that this influence on the contrast threshold decreases as the distance to the adaptation section increases. Hence our results suggest mechanisms within the visual system mathematically best described by a local spectrum analysis.
Adaptation, Ocular↗
Displacement of Chernobyl fallout in snow layers of temperate Alpine glaciers.
Measurements of the gross-beta-activity and a gamma-spectrum analysis of radioactive fallout from Chernobyl distributed in vertical snow profiles on an Alpine glacier were carried out. Samples were collected in summer 1986 and in summer 1987. A displacement of isotopes to depths of approximately 6 m was observed. The mean activity per unit area amounts to 10.4 and 6.6 kBq m-2 for samples from 1986 and 1987, respectively, both values corrected to 1 May 1987. Isotopes with half-lives shorter than 110m Ag (250 days) could no longer be detected in 1987.
Accidents↗
Effects of nonsedating histamine H1-antagonists on EEG activity and behavior in the cat.
The central effects of the newly-developed antihistamines (H1-receptor antagonists) loratadine, astemizole, mequitazine and terfenadine were evaluated by studying brain electrical activity (EEG), sleep-waking patterns and behavior in the cat. The different stages of the sleep-waking cycle, i.e., wakefulness (W), spindle sleep (SS), slow wave sleep (SWS) and REM sleep (REM) were evaluated. The power spectrum analysis of the EEG was obtained by a computerized technique. For comparison, the sedating agent diphenhydramine was examined. Given at 3 mg/kg orally, a dose slightly above that effective therapeutically, diphenhydramine markedly affected behavior and all sleep stages. In particular, it depressed REM and increased SS (drowsiness). The EEG showed occasional spikes typical of subconvulsive states. Loratadine did not modify either sleep patterns or behavior over the 3-30 mg/kg dose range orally, which is far above that used clinically. The EEG, evaluated either visually or by spectral power analysis, was unaffected. Astemizole at 10 and 30 mg/kg PO reduced REM, markedly altered behavior at 30 mg/kg, but did not modify EEG activity. Mequitazine, at low doses (1-10 mg/kg PO), enhanced SS and decreased SWS and REM. Like diphenhydramine, mequitazine induced EEG changes typical of subconvulsive states and affected EEG power over the frequency range of 0.1-15.0 Hz. Terfenadine did not change sleep patterns and slightly affected behavior only at the high dose of 30 mg/kg orally; EEG activity was not influenced. These data show that: a) diphenhydramine and mequitazine appear to produce CNS effects by altering basic processes within the brain; b) astemizole and terfenadine seem to cross the blood-brain barrier at high doses only; c) loratadine has the lowest liability to produce central side effects. Of the sleep features examined, REM appeared to be the most sensitive stage to blockade of central H1-receptor pathways.
Animals↗
Molecular interface characterization in human bone matrix. I. Biochemical and IR spectroscopic studies.
The aim of this work is the characterization of interfaces in calcified tissues. In order to separate the non-collagenous bone proteins, according to their interaction with collagen or hydroxyapatite crystals, 10 sequential bone demineralizations using EDTA alone were carried out, followed by four sequential extractions using both EDTA and GuHCl. The extracts were characterized by SDS-PAGE, IR spectrum analysis, and kinetics of demineralization and proteins released. A great proportion of non-collagenous proteins are bound to the collagen matrix, many of which have a high affinity to it. This work demonstrates that collagen is not directly linked to the mineralized phase.
Adult↗
Optimal frequency ranges for extracting information on autonomic activity from the heart rate spectrogram.
Heart rate variability spectrum analysis provides useful quantitative indices of neural control of the SA node. This method is attractive both for its simplicity and the lack of invasive instrumentation, particularly for human investigation. The differing spectral characteristics of parasympathetic and sympathetic control of heart rate allows separate measurement. However, there are widely varying opinions as to the appropriate frequency bands to represent these two inputs. We compared the heart rate variability spectra of 16 humans in supine and upright positions. Adequate measures of parasympathetic or sympathetic activity change should correlate respectively inversely or directly with heart rate change. Frequently used spectral measures of sympathetic activation did not correlate with heart rate changes. With optimization of frequency bands, we found that restricting the sympathetic band to frequencies below 0.1 Hz and above 0.05 Hz (0.055 to either 0.086-0.098 Hz), and dividing by total spectral amplitude 0.004-0.5 Hz (to account for parasympathetic fluctuations within the sympathetic band) produced the best results. The parasympathetic band was best from 0.1 Hz to a frequency greater than that of the respiratory sinus arrhythmia. The optimization method detailed here is easily applied to circumstances other than active orthostasis, and should provide a means of empirically determining useful frequency limits.
Adolescent↗
Long-lasting afterdischarge of alpha-motoneurons after muscle vibration or electrical stimulation of group I afferent fibers in the anemically decerebrated cat.
Experiments were performed on anemically decerebrated cats. Motoneuronal activity in the spinal cord was intracellularly or extracellulary recorded and muscle vibration or electrical stimulation of the peripheral nerve was applied for 1 s every 2 s. Such stimulation elicited monosynaptic responses and afterdischarge, a response which lasts after cessation of the stimuli. Stimulus frequencies from 50 to 200 Hz were effective in eliciting the afterdischarge, while frequencies higher or lower than this range of stimulation were ineffective. The interspike intervals of the motoneuron afterdischarge were almost constant and did not correspond to the stimulus frequency. The mean intervals obtained from the motoneurons examined ranged from 70 to 120 ms. Power spectrum analysis of the membrane potential ripples recorded immediately after stimulation revealed increased activity at 38 and 62 Hz components. Since the spike interval of the afterdischarge in this motoneuron was 80 ms, the interval was almost equal to 5- and 3-fold the cyclic time of the increased frequency components. This indicates that the interval of afterdischarge was determined by the specifically increased frequency components of the membrane potential ripples.
Animals↗
Methods for the identification of evoked response components in the frequency and combined time/frequency domains.
Two prominent frequency components designated f1 and f2 have been identified in the visual evoked response to the transient presentation of sinusoidal luminance gratings in the range of 0.5-8 c/deg. The components occur at temporal frequencies below the alpha band, with the f1 frequency being roughly half that of the f2 frequency. The f1 component is largest at low spatial frequencies with f2 becoming progressively dominant as spatial frequency is increased. The frequency and amplitude of f1 and f2 change substantially over the time course of the response. This has been studied by calculating the temporal frequency spectrum of the transient evoked potential over successive short-time epochs running through the response. Using this technique, the response is shown to consist of narrow-band frequency peaks or 'formants' emerging at different times after stimulus onset. These formants occur at frequencies other than those of the spontaneous EEG and undergo changes in frequency and amplitude over the time course of the response. Two spectrum analysis techniques were employed: the Discrete Fourier Transform and Linear Predictive Coding. Frequency components were successfully identified in single-trial responses using the LPC technique.
Electroencephalography↗
Multiple effects of CD4 CDR3-related peptide derivatives showing anti-HIV-1 activity on HIV-1 gp120 functions.
The interaction of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 with CD4 CDR3-related peptide derivatives showing anti-HIV-1 activity has been studied. Conformational changes in gp120, which could affect its interaction with CD4 and its shedding from virions, were detected by fluorescence spectrum analysis of tryptophan residues after addition of peptide representative of the CD4 CDR3-related region, but not the CD4 CDR2-related region. Interestingly, the addition of scrambled peptide, S1 (with altered amino acid sequence compared with the native CDR3-related peptide but unaltered overall composition), which we recently showed to have stronger anti-HIV-1 activity than the original CDR3-related peptide, had no effects on the conformational change in gp120 or on its interaction with CD4 and its shedding from HIV-1 virions. However, all of the CDR3-related peptides, including S1, showed blocking effects on the binding of antibodies against gp120 V3 loop and C-terminus regions. Thus, we concluded that there were at least two separable activities of the CDR3-related peptides in anti-HIV-1 activity, i.e. induction of conformational changes in gp120, which could affect its binding to CD4 and to gp41 (as observed in native CDR3-related peptides), and inactivation of V3 loop and C-terminus regions in gp120 (as observed in all of the CDR3-related peptides, including S1).
Amino Acid Sequence↗
Isolation and structure determination of natural analogues of the mycotoxin ochratoxin A produced by Aspergillus ochraceus.
Three new natural mycotoxins, analogues of ochratoxin A, in which the phenylalanine moiety is replaced by serine, hydroxyproline or lysine, were isolated from cultures of Aspergillus ochraceus by TLC followed by HPLC column chromatography. Their structures were determined after acidic hydrolysis by the characterisation of both their amino acid moieties and of ochratoxin alpha, the chlorinated dihydroisocoumarin moiety of ochratoxin A. These structures were confirmed by mass spectrum analysis.
Aspergillus ochraceus↗
Fetal and maternal aortic flow in two different maternal positions. An investigation with combined Doppler-velocimetry and ultrasonic multiple array.
To study aortic velocities in the fetus, a newly developed multirangegated Doppler velocimeter was combined with a commercial B-mode linear-array apparatus. Spectrum analysis of the Doppler shift signals was performed. The signals with the highest frequencies were selected for hard-copy, and integrated with a digitizer. In the first part of the study, the reproducibility of the method was established by serial measurements of aortic velocity in 7 near-term fetuses. It proved sufficient to evaluate 5 successive heart-cycles. The mean coefficient of variation was 5% (mean number of recordings evaluated 7.5). In the second part of the study, possible influence of aortocaval compression on fetal aortic velocity indicative of changes in fetal cardiac output, was investigated in 10 pregnant women with no symptoms of supine hypotension. Doppler monitoring of the material cardiac output from the suprasternal notch was added to the set-up described to study the supine reduction of cardiac output frequently described in pregnant women. No significant change was found either in the maternal or in the fetal circulation.
Aorta↗
Acquisition and processing of the radio-frequency signal in echocardiography: a new global approach.
Recently there has been an increasing interest in the use of the "raw" radio-frequency (RF) signal generated in echocardiography for use in tissue-characterization to distinguish between normal and pathological myocardium, for automatic delineation of the endocardial border without being limited by the weak contrast of the traditional video images, and for use in contrast echography, where it could offer the possibility to visualize perfusion using intravenous contrast injections. One of the main problems in this kind of research is the acquisition of the signal having a high frequency and large bandwidth. We have developed a new global method for the acquisition of this RF signal. To digitize the data, a video sequencer is used. In this way it becomes possible to sample all available data generated by the echographic equipment during at least 1 s. This means that all data of the complete sector scan during a complete heart-cycle can be digitized without using any data reduction technique or triggering on the electrocardiogram. The advantage of this approach is that all characteristics of the signal can be studied, without being limited by data reduction techniques used during acquisition. This method enables us to calculate parameters such as "integrated backscatter," or to investigate the signal more extensively, e.g., by using spectrum analysis. We can compare different regions of the myocardium and examine them during the heart-cycle, all within the same beat. We have also written a software package for the processing of the large amount of data resulting from the acquisition.
Animals↗
Effect of vitamin E on acetylcholine-induced current in molluscan neurons: role of cytoplasmic free calcium and arachidonic acid.
Role of cytoplasmic concentration of free Ca2+ ([Ca]in) and arachidonic acid in potentiating the effect of vitamin E (DL-alpha-tocopherol) on acetylcholine receptor activity in Helix pomatia neurons was studied using a two-microelectrode intracellular recording, voltage clamp and fluorescent calcium probe fura-2 technique. Elevation of [Ca]in by intracellular injection from a microelectrode or by depolarizing pulses and application of 0.1 microM-0.1 mM vitamin E enhanced the acetylcholine-induced chloride current both in LP11 and RBc4 neurons. Application of 10 microM arachidonic acid to the same neurons decreased this current. The use of fluorescent probe showed that vitamin E did not essentially change [Ca]in, but an increase of [Ca]in intensified both the enhancing effect of vitamin E and the depressing effect of arachidonic acid. The enhancing effect of calcium influx was considerably decreased after vitamin E application. The antioxidant action of vitamin E was probably not involved in the mechanism of its enhancing effect on acetylcholine-induced current, since synthetic antioxidant, ionol, depressed acetylcholine responses. A spectrum analysis has shown the interaction between vitamin E and arachidonic acid in solution. This interaction may be considered as the molecular mechanism responsible for the prevention by vitamin E of steady arachidonic acid production from membrane phospholipids and its down-regulatory effect on acetylcholine receptor activity. Our results support this suggestion, since an inhibitor of phospholipase A2, 4-bromophenacyl bromide, mimicked the enhancing effect of vitamin E.
Acetylcholine↗
Multivariate data analysis of NMR data.
Multivariate methods based on principal components (PCA and PLS) have been used to reduce NMR spectral information, to predict NMR parameters of complicated structures, and to relate shift data sets to dependent descriptors of biological significance. Noise reduction and elimination of instrumental artifacts are easily performed on 2D NMR data. Configurational classification of triterpenes and shift predictions in disubstituted benzenes can be obtained using PCA and PLS analysis. Finally, the shift predictions of tripeptides from descriptors of amino acids open the possibility of automatic analysis of multidimensional data of complex structures.
Amino Acid Sequence↗
Intraoperative duplex scanning of arterial reconstructions: fate of repaired and unrepaired defects.
PURPOSE: Because unrecognized lesions can cause an arterial reconstruction to fail, duplex ultrasonography was evaluated as an intraoperative aid to assess technical adequacy and provide criteria for which lesions should be repaired immediately versus safely followed. METHODS: Since 1990 intraoperative color duplex scanning(7 to 10 MHz linear array probe, pulsed-wave Doppler test spectrum analysis) was used to assess the frequency and severity of residual lesions in 368 patients after carotid endarterectomy (n = 210), infrainguinal vein bypass (n=135) or visceral/renal reconstruction (n = 23). Duplex scan results were categorized as normal or abnormal, with immediate repair of lesions demonstrating both lumen reduction and severe focal flow abnormalities (peak systolic velocity [Vp] > 150 to 180 cm/sec;velocity ratio [Vr] > 2.4). Arteriography was also performed in 81% of lower limb bypass procedures. RESULTS: Duplex scanning identified technical (residual plaque, stricture) or intrinsic defects (platelet thrombus, distal thrombosis) requiring revision in 37 (10%) of the reconstructions. Infrainguinal bypass had the highest incidence of corrected defects (14%) and adverse events (3%). No adverse events occurred in patients with normal duplex scan results or after carotid endarterectomy. Overall, 76% of identified defects were corrected (carotid, 17 of 24; infrainguinal bypass, 19 of 24; visceral bypass, 1 of 1). Unrepaired flow defects (Vp = 150 to 190 cm/sec; Vr = 1.8 to 2.5) led to one graft occlusion and three early revisions. Postoperative duplex scanning demonstrated residual stenosis in seven of 12 patients with unrepaired defects, two of 36 patients with repaired defects, and five of 312 patients with normal scan results (p < 0.001). CONCLUSION: Based on the types of lesions corrected and the low (< 0.5%) complication rate after a normal or modified arterial reconstruction, duplex scanning was found to be a valuable intraoperative aid. Unrepaired defects require close surveillance for progression.
Algorithms↗
Spectra and structure of alpha-tocopherol radicals produced in anoxic media.
Electron spin resonance and flash photolysis studies have been combined to determine, amid conflicting reports from radiolysis studies, the spectrum for the phenoxyl radical of alpha-tocopherol. Triplet state ketones were used to abstract the alpha-tocopherol phenolic hydrogen in order to obtain both the transient ESR spectrum and optical spectrum. Analysis of the ESR data yields g = 2.00469, a(H, 5-CCH3) = 6.04G, a(H,7-CCH3) = 4.51G, a(H, CH2) = 1.38G, a(H', CH2) = 1.49G, and a(H,8-CCH3) = 0.89G. The g factor shows large spin population on oxygen in this radical and demonstrates conclusively involvement of the phenoxyl radical. Both spectra were in agreement with those produced by radiolysis of alpha-tocopherol in N2 saturated EtOH. While the spectral characteristics of the phenoxyl radical now appear to be clarified, uncertainties remain concerning optical spectra for radiolysis of alpha-tocopherol in air- and oxygen-containing systems.
Anaerobiosis↗
Renin-angiotensin-aldosterone system, RR interval, and blood pressure variability during postural changes in borderline arterial hypertension.
This study aimed to examine the changes in RR interval and blood pressure (BP) variability and humoral factors during postural changes in borderline arterial hypertension. Twenty-nine patients (44 +/- 3 year; BP, 145 +/- 3/84 +/- 3 mm Hg) with borderline hypertension and a control group of 38 subjects (35 +/- 2 year; BP, 123 +/- 3/70 +/- 2 mm Hg) underwent power spectrum analysis of RR interval and BP (low frequency (LF), 0.05 to 0.15 Hz; high frequency (HF), 0.15 to 0.40 Hz) in the supine and standing positions. Concentrations of plasma renin activity, angiotensin II, and aldosterone in supine and standing positions had been determined in the hypertensive group. Borderline hypertensives are characterized by higher oscillations of systolic and diastolic BP, but not of RR interval in the supine position versus the control group. Low frequency and HF components of systolic and diastolic BP expressed as absolute data are also significantly higher in borderline hypertensives. Moreover, standing tended to increase the LF/HF ratio of both RR interval and BP variability compared to controls. The standing position was able to further activate the LF but not the HF component of BP variability. In borderline hypertension renin release during postural changes correlated well with the decrease in the power of the HF vagal component of RR interval variability (r = -0.70, P < .001) and with the increase of the LF component of diastolic blood pressure variability (r = 0.43, P = .03). In conclusion, our results indicate that in borderline arterial hypertension, LF and HF oscillations of BP are already significantly increased at rest.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Is respiratory sinus arrhythmia present in atrial fibrillation? A study using two quantitative methods.
Two quantitative techniques have been evaluated to examine whether respiratory sinus arrhythmia can be detected in atrial fibrillation. Cyclical changes in heart rate during deep breathing indicating respiratory sinus arrhythmia were seen in 11/15 control patients, but only 1/44 patients with atrial fibrillation. Power spectrum analysis suggested that more subtle variations in heart rate with breathing may be present in some patients with atrial fibrillation where it was not detectable by simpler techniques. These results support the hypothesis that although respiratory sinus arrhythmia is not detectable in atrial fibrillation by conventional means, there may still be some mediation of heart rate either by vagal or extravagal mechanisms.
Aged↗