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Detailed evidence of cerebral haemoglobin oxygenation in response to motor cortical activation revealed by a continuous wave spectrophotometer with 10 Hz temporal resolution
No full textEvaluation of potential factors affecting the measurement of cerebrovascular reactivity by near-infrared spectroscopy
No full text1. Near-infrared (IR) spectroscopy is based on the relative transparency of skin, skull and brain to the light in the near-IR region (700-1100 nm) and on the oxygen-dependent tissue absorption changes of haemoglobin. 2. We evaluated the most relevant factors (reproducibility, venous return, age and sex) that might affect reliability of near-IR spectroscopy to test CO2 cerebrovascular reactivity. 3. Thirty-four healthy volunteers were enrolled in the study. The protocol consisted of a 3-min baseline, a 3-min hypercapnia (5% CO2 in air) and a 2-min recovery. Transcranial Doppler sonography measurements were simultaneously performed. The CO2 reactivity test was repeated on 27 subjects after 1 h to assess reproducibility. CO2 reactivity was also evaluated at different body positions (supine, 35 degrees Trendelenburg and 35 degrees reverse Trendelenburg), and over a gradual increase of the inspired CO2. 4. Changes in near-IR spectroscopy and transcranial Doppler sonography parameters were significantly correlated with variations of end-tidal CO2 (P 0.05). The reactivity index of oxyhaemoglobin and deoxyhaemoglobin decreased (P < 0.05) and increased (P < 0.01) with age respectively. 5. We found that near-IR spectroscopy is a reliable and reproducible method for the evaluation of cerebrovascular reactivity and might be considered, after appropriate validation, for the assessment of patients with cerebrovascular disease
A minimal cavity and its capacitive coupling for in vivo EPR measurements on mice.
No full textA very simple ring resonator for in vivo L-band EPR spectroscopy was built and characterised. It employs a special capacitive coupling that allows measurents to be made on large biological samples which are not possible with other resonators. In spite of its intrinsic low Q it has a sensitivity almost equivalent to that obtained from high Q resonators. These features were tested down to a nitroxide concentration of 10 mu M in high conductivity phantoms
From continuous wave to frequency-domain near infrared spectroscopy for absolute quantification of the chromophora
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Cerebral hemoglobin oxygenation in response to motor cortical activation revealed by a fast spectrophotometer
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Energy metabolism and interstitial fluid displacement in human gastrocnemius during short ischemic cycles
No full textEnergy metabolism and interstitial fluid displacement were studied in the human gastrocnemius during three subsequent 5-min ischemia-reperfusion periods [ischemic preconditioning (IP)]. The muscle energy balance was assessed by combining near-infrared spectroscopy (NIRS) and P-31-nuclear magnetic resonance spectroscopy (P-31-NMRS). The interstitial fluid displacement was determined by combining NIRS and Na-23-NMRS. No changes in total energy consumption or in the fractional contribution of the underlying energy sources (aerobic glycolysis, anaerobic glycolysis, and Lohmann reaction) were observed in the muscle during the tested IP protocol. Oxygen consumption in the muscle region of interest, as estimated by NIRS, was similar to 8 mu mol . 100 g(-1) min(-1) and did not change during IF. Phosphocreatine and ATP concentrations did not change over the whole experimental period. A slight but significant (P < 0.05) increase in intracellular pH was observed. Compared with the control, a 10% greater interstitial fluid content per muscle unit volume was observed at the end of the IP protocol. It is concluded that, at variance with cardiac muscle, repeated 5-min ischemia-reperfusion cycles do not induce metabolic changes in human gastrocnemius but alter the interstitial fluid readjustment. The techniques developed in the present study may be useful in identifying protocols suitable for skeletal muscle preconditioning and to explain the functional basis of this procedure
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