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Biomedical subjects

C Fieschi

Publications and source records attributed to C Fieschi.

At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

Simplified, noninvasive PET measurement of blood-brain barrier permeability.

Blood-brain barrier (BBB) permeability to [68Ga]EDTA was measured by positron emission tomography (PET) in four normal volunteers and in 11 patients with brain tumors. A unidirectional transfer constant, Ki, was calculated applying multiple-time graphical analysis (MTGA). This method allows the detection of backflux from brain to blood and, by generalization, the measurement of the constant Kb (brain to blood). Furthermore, the need for an independent measurement of the intravascular tracer is obviated: MTGA itself provides an estimate of the cerebral plasma volume (Vp). In the four normal volunteers the Ki was 3.0 +/- 0.8 X 10(-4) ml g-1 min-1 (mean +/- SD) and the Vp 0.034 +/- 0.007 ml g-1. A net increase in Ki up to a maximum of 121.0 X 10(-4) ml g-1 min-1 (correspondent value of Kb = 0.025 min-1) as well as an increase of Vp was observed in malignant tumors. The input function was calculated using both the [68Ga]EDTA concentration in sequential arterial blood samples and, noninvasively, the activity derived from the superior sagittal sinus image. The values of Ki and Vp from these two calculations were in good agreement. The application of MTGA to PET permits the evaluation of passage of substances across the BBB without making assumptions about the compartments in which the tracer distributes.

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PubMedDate not supplied

Autonomic nervous activity during sleep in middle cerebral artery infarction.

No data are available on the autonomic system during sleep in patients with stroke. The purpose of this study was to determine the influence of acute ischemic stroke on the autonomic cardiovascular system during sleep, and to correlate autonomic activity with the clinical status of patients. Ten patients with ischemic stroke in the middle cerebral artery were studied by means of an all-night polysomnographic recording within the 1st week of the onset of symptoms and at the 3-week follow-up examination. Power spectrum analysis of the heart rate variability was performed using an autoregressive algorithm in 180 consecutive electrocardiographic RR intervals. Spectral power was calculated in 3 main frequency bands: high frequency (HF), 0.15-0.4 Hz; low frequency (LF), 0.04-0.15 Hz; very low frequency (VLF), < 0.04 Hz. The data were compared with those of 10 age-matched controls. A significant increase in VLF (p < 0.0005) and a decrease in HF (p < 0.0002) components were found in ischemic stroke patients. The sympathetic-parasympathetic balance (VLF + LF/HF) was higher in patients than controls (p < 0.005). However, these components changed significantly during sleep, revealing a physiological pattern. These power spectral data were still present at the 3-week follow-up. The 4 patients who developed cardiac arrhythmias showed higher sympathetic-parasympathetic balance than patients without arrhythmias (p < 0.05). These data suggest a sympathetic predominance in patients with acute ischemic stroke during sleep. However, the flexible and dynamic properties of the autonomic nervous system are preserved. Cardiac arrhythmias following stroke may be related to the degree of sympathetic predominance.

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