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At least 199 records · Page 11Linked to original sources
PubMed2003

Fast cerebral functional signal in the 100-ms range detected in the visual cortex by frequency-domain near-infrared spectrophotometry.

Brain activity is associated with physiological changes, which alter the optical properties of the tissue in the near-infrared part of the spectrum. Two major types of optical signals following functional brain activation can be distinguished: a slow signal due to hemodynamic changes and a fast signal, which is directly related to neuronal activity. The fast signal is small and therefore difficult to detect. We used a specially noise-optimized frequency-domain near-infrared spectrometer with a pi-sensor, which was expected to be particularly sensitive to deeper tissue layers, to investigate the human visual cortex during visual stimulation generated by a checkerboard. We were able to detect significant fast signals in single light bundles, but not in pi-signals. The fast signals were mostly collocated with strong slow hemodynamic signals, but showed a higher degree of localization than the latter. The latencies of 40 +/- 16 ms of the fast signals were similar between locations. Our results also indicate that the brain responds differently to a single and double (forth and back) reversal of the checkerboard, with a stronger reaction upon the double reversal.

Adult↗
PubMed2001

Quantitative analysis of active compounds in pharmaceutical preparations by use of attenuated total-reflection Fourier transform mid-infrared spectrophotometry and the internal standard method.

A new method is presented for the quantitative analysis of compounds in pharmaceutical preparations Fourier transform (FT) mid-infrared (MIR) spectroscopy with an attenuated total reflection (ATR) module. Reduction of the quantity of overlapping absorption bands, by interaction of the compound of interest with an appropriate solvent, and the employment of an internal standard (IS), makes MIR suitable for quantitative analysis. Vigabatrin, as active compound in vigabatrin 100-mg capsules, was used as a model compound for the development of the method. Vigabatrin was extracted from the capsule content with water after addition of a sodium thiosulfate IS solution. The extract was concentrated by volume reduction and applied to the FTMIR-ATR module. Concentrations of unknown samples were calculated from the ratio of the vigabatrin band area (1321-1610 cm(-1)) and the IS band area (883-1215 cm(-1)) using a calibration standard. The ratio of the area of the vigabatrin peak to that of the IS was linear with the concentration in the range of interest (90-110 mg, in twofold; n=2). The accuracy of the method in this range was 99.7-100.5% (n=5) with a variability of 0.4-1.3% (n=5). The comparison of the presented method with an HPLC assay showed similar results; the analysis of five vigabatrin 100-mg capsules resulted in a mean concentration of 102 mg with a variation of 2% with both methods.

Anticonvulsants↗
PubMed1996

Regional cerebral oxygen saturation during electroconvulsive therapy: monitoring by near-infrared spectrophotometry.

Electroconvulsive therapy (ECT) increases neuronal energy consumption and alters systemic hemodynamics. We examined the effects of ECT on regional cerebral oxygen saturation (rSo2) using a near-infrared spectro-photometer. Heart rate (HR), mean arterial blood pressure (MAP), and rSo2 were continuously monitored throughout ECT under general anesthesia in 43 patients. In all subjects, rSo2 changed in a consistent pattern during ECT, initially decreasing (-9.4% +/- 0.9%) just after application of the electrical current and subsequent increasing (8.7% +/- 0.9%) beyond the pre-ECT value. A close correlation was demonstrated between the increase in rSo2 and the mean blood pressure after the electrical shock (r2 = 0.832, P < 0.0001). We conclude that ECT initially may increase cerebral metabolic rate of oxygen more than cerebral blood flow and that rapidly increasing blood pressure transiently may overwhelm cerebral pressure autoregulation.

Anesthesia, General↗
PubMed2000

[Analysis of urinary calculi in adults from the Moroccan Medium Atlas by Fourier transform infrared spectrophotometry].

OBJECTIVE: To determine the stone composition in adult patients from the medium Atlas of Morocco. MATERIAL AND METHODS: A series of 183 calculi from adult patients (males: 123, females: 60) collected in medium Atlas of Morocco was analysed by Fourier Transform infrared spectroscopy. The stones were surgically removed (n = 168) or spontaneously passed (n = 15). RESULTS: Kidney stones are encountered in 70.5% of calculi. The stones were twice frequent in males than in females (M/F = 2.10). Whewellite was the main component in 51.4% of the stones and 49.7% of the stone core, weddellite in only 7.1% of stones and 6.4% of the nuclei. Uric acid was predominant in 18% of stones and also 19.7% of nuclei, and carbapatite in 12.6% of stones and nuclei. All in all, whewellite was present in 77.6% of calculi and weddellite in 25.1%, carbapatite in 68.3% and PACC in 23.5%, struvite in 15.3%, uric acid in 20.8% and ammonium hydrogen urate in 14.2% of cases. Struvite stones were more frequent in females and uric acid calculi in males, in particular in patients aged more than 60 years old. CONCLUSION: As observed in most countries, calcium oxalate was the most frequent major component of the stones (58.5%). Uric acid stones were more frequent (18%) than reported in Western countries, thus suggesting that particular dietary habits are involved in stone formation. The relatively high occurrence of struvite stones (8%) could be a marker of an insufficient early detection and treatment of chronic urinary tract infection.

Female↗