To estimate changes in regional cerebral blood flow (rCBF) without arterial sampling in the study of functional-anatomical correlations in the human brain, using (15)O-labeled water and PET, a standard arterial input function was generated from the input function in 10 normal volunteers with dose calibration and peak time normalization. The speed and volume of injection were precisely controlled with a mechanical injector. After global normalization of each tissue activity image, the standard arterial input function was applied to obtain estimated CBF images. Relative changes in estimated rCBF to whole brain mean CBF(DeltaFest) and those in regional tissue activity (DeltaC) were compared with true relative rCBF changes (DeltaF) in 40 pairs of images obtained from 6 normal volunteers. DeltaFest correlated well with DeltaF, whereas DeltaC consistently underestimated DeltaF. This noninvasive method simplifies the activation studies and provides the accurate estimation of relative flow changes.
1. The effects of ouabain and acetazolamide on the secretion of pancreatic juice stimulated by secretin in anaesthetized dogs were investigated. 2. Intra-arterial injection of ouabain (1-10 micrograms) and acetazolamide (1-10 mg) caused dose-dependent decreases in the volume of pancreatic juice. When both drugs were added together, the inhibitory effects were significantly higher than for each drug alone. 3. The bicarbonate concentration in the pancreatic juice was decreased and the chloride concentration was increased by ouabain and acetazolamide, but sodium and protein concentrations were not modified. 4. The results suggest that the Na+,K+-ATPase and carbonic anhydrase activities play important roles in water and electrolyte secretion, and that ouabain and acetazolamide inhibit secretin-stimulated pancreatic secretion by acting on different systems in the exocrine cells in dogs.
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