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Slices of frog cerebrum, optic tectum, medulla and spinal cord rapidly accumulate [3H]GABA and [3H]glycine from the surrounding medium so that after 10 min tissue:medium ratios as high as 113 for GABA (optic tectum) and 18.5 for glycine (medulla) may be achieved. Kinetic analysis revealed two distinct saturable uptake systems for each amino acid in the 4 CNS areas. The high affinity systems (apparent Km: 9-22 muM for GABA; 5-35 muM for glycine) required sodium ions in the medium and were relatively substrate specific. Significant release of [3H]GABA and [3H]glycine, but not of L-[3H]leucine, was evoked by exposure to medium containing potassium ions in a concentration of 40 mM. The process of release was calcium-dependent. The importance of these results with regard to the roles of GABA and glycine as neurotransmitters in both spinal and supraspinal levels of the amphibian neuraxis is discussed.

Hematocrit determinations by microhematocrit and electronic particle counter technics were obtained using newborn and adult blood samples. Coulter Model S hematocrit values greater than .47 were found to be significantly lower than those obtained by using the microhematocrit technic. These differences assume clinical importance when considering partial plasma exchange transfusion for the treatment of polycythemia and associated hyperviscosity.