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At least 1,765 records · Page 98Linked to original sources
PubMed1984

[Echotomography and spectral analysis of the Doppler signal in the assessment of carotid lesions].

Real-time echography and C.W. Doppler examination with spectrum analysis are the two methods most widely used for the study of the circulation. Echography allows the detection and the localization of the atheromatous defects whereas Doppler examination provides information on the blood flow. With the help of the frequency analysis of the Doppler signal it is possible to study much more accurately the local haemodynamic conditions. Spectrum analysis is one of the possible display mode for the Doppler signal. It provides in comparison with the zero crossing mode, much more haemodynamic parameters on the blood flow, such as velocity spectrum, density of red cells on each velocity... In this study, we tried to demonstrate that a relationship exists between the amplitude of the spectrum disturbances, recorded just after a stenosis and the degree of this stenosis. For that we propose a classification of the spectrum disturbances in five grades, each of them being related to an interval of possible values for the stenosis degree (grade I----stenosis less than 40% in area, grade II----40-60% stenosis, grade III----60-75% stenosis (extended defects) grade IV----70-90% (extended defects) and 60-90% short stenosis. Grade V: stenosis greater than 90%. The results provided by this classification were compared to those obtained by measurements of the stenosis degree on the piece of endarterectomy (72 cases). The results were in agreement in 94% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriosclerosis↗
PubMed1984

Oxygen metabolism in cloned macrophage cell lines: glucose dependence of superoxide production, metabolic and spectral analysis.

The requirements of a cloned macrophage-like cell line, J774.16, for oxygen metabolism, and the nature of the defect in oxidative metabolism in a variant clone derived from it, J774.C3C, were studied. Upon stimulation with phorbol myristate acetate (PMA), the parental clone produced approximately 1 nmol O2-/min/10(6) cells, whereas the variant clone produced no detectable O2- under the same conditions. Sustained O2- production by J774.16 was totally dependent on extracellular glucose; in glucose-free medium, the cells initiated O2- production but could not sustain it. When cells were stimulated with PMA, glucose-C-1 oxidation of J774.16 cells increased 20-fold while that of J774.C3C remained at resting levels. O2- production in J774.16 cells was inhibited by some agents known to block mitochondrial electron transport before coenzyme Q, such as rotenone and tetrathiafulvalene, whereas antimycin A enhanced O2- production. A dissociation between O2- production and glucose-C-1 oxidation was observed when J774.16 was treated with certain metabolic inhibitors. Quinacrine, 2,4-dinitrophenol, chlorpromazine, and trifluoperazine inhibited O2- production completely under conditions in which glucose-C-1 oxidation was reduced only by 30%. Rotenone inhibited O2- production with no effect on glucose-C-1 oxidation whereas antimycin A augmented O2- production 50% but inhibited glucose oxidation by 20%. Glucose transport studies, with 2-deoxy-D-glucose, showed that the Km for glucose transport of both clones was about 1 mM, indicating that cells could effectively transport glucose even at low concentrations. The Vmax for glucose transport in both J774.16 and variant J774.C3C cells doubled after PMA stimulation, indicating that the variant was effectively stimulated by PMA, even though O2- was not produced. Similarly, PMA induced protein phosphorylation in both clones. No differences between clones J774.16 and J774.C3C in hexokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione reductase, or glutathione peroxidase activities could be found. When dithionite-reduced and -oxidized difference spectra of plasma membranes of these clones were compared, comparable levels of b-type cytochrome were found in both clones. However, CO difference spectra indicated that CO was bound to a b-type cytochrome (presumed to be b-245) in clone J774.16 but not in J774.C3C.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Plasma levels of alfentanil and etomidate in patients and their relation to compressed power spectral analysis of the EEG.

In 22 patients alfentanil-etomidate anesthesia was used for orthopedic procedures using for the induction period 300 micrograms/kg of the hypnotic and 100 micrograms/kg of the opioid. Maintenance of anesthesia consisted of 20 micrograms/kg of alfentanil given every 15 min and 20 micrograms/kg/min of etomidate given over an infusion. The patients were intubated and mechanically ventilated with pure oxygen. In order to access the state of vigilance with respect to etomidate and alfentanil plasma levels, EEG power spectra were computed from electrical cortical activity of the occipital region (P3-O1); respectively venous blood samples were assayed by means of gas chromatography for alfentanil and etomidate plasma concentration. In the EEG power spectrum, anesthesia replaced the high dominant alpha-peaks of the control-awake period by a disharmonious pattern over the whole frequency range (0.5-16.0 Hz). At the end of anesthesia vigilance recording indicated a correlation with plasma etomidate level. Once concentration had dropped below 100 ng/ml power spectra were characterized by a stable harmonious peak in the alpha-range (8.0-10.0 Hz). Plasma levels above 100 ng/ml induced a fluctuating pattern with peaks in the theta to delta band (0.5-8.0 Hz); the latter was characterized by drowsiness and a reduced respiratory drive. Opioid plasma levels above 100 ng/ml with etomidate levels below 80 ng/ml did not influence to the same extent. EEG power spectra seem to be a useful tool in pinpointing to a reduced state of vigilance. Such a state when present with opioid ingestion is often accompanied by respiratory depression.

Adult↗