The percentages of 22 14C-labeled amino acids remaining in rat brain 15 s after carotid injection were measured relative to a simultaneously injected diffusible internal standard, 3HOH. The injected solution also contained a nondiffusible internal standard, [113mIn]EDTA to correct for incomplete brain blood compartment washout. Self-inhibition and cross-inhibition was demonstrated by inclusion of unlabeled amino acids and carboxylic acids. All amino acids tested, excluding proline, alanine, and glycine, could be assigned to one, and only one, blood-brain barrier carrier system. The neutral carrier system transported phenylalanine, leucine, tyrosine, isoleucine, methionine, tryptophane, valine, DOPA, cysteine, histidine, threonine, glutamine, asparagine, and serine. Affinity for a basic amino acid carrier system was demonstrated for arginine, ornithine, and lysine. A third, low-capacity independent carrier system transporting aspartic and glutamic acids was demonstrated.

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A new method is developed for the measurement of the radii of curvature R of mirror-like semiconductor wafers using the magic-mirror (Makyoh) method. A flat mirror is placed beneath the sample, thus a second, “contour” image of the sample is formed beside the sample image itself. From the size deviation of the two images that results from the curvature of the sample, R can be calculated. Experimental results obtained with mirrors with known curvature show good agreement with the calculations. Implications for the general image formation mechanism are discussed as well.