Cysteine sulfinate decarboxylase (CSD; EC 4.1.1.29) activity from porcine brain was resolved into three peaks by hydroxylapatite chromatography. The first two peaks (I and II) did not decarboxylate and were not inhibited by glutamate. The third peak (III) cochromatographed with glutamate decarboxylase (GAD; EC 4.1.1.15) activity. The Km values of cysteine sulfinate for peaks I, II, and III were 5.5 × 10−4m, 1.3 × 10−4m, and 4.5 × 10−3m, respectively. The possibility that the same enzyme was responsible for peak III CSD and GAD activities was suggested by several findings: (1) Mutual competitive inhibition was observed between glutamate and cysteine sulfinate for these activities. (2) Similar first‐order heat‐inactivation curves were obtained for peak III CSD and GAD when incubated at 55xBOC. (3) Both activities were inhibited similarily by ATP and chloride ion. High concentrations of glutamate (0. l m) inhibited peak III CSD activity more than 90% but had no effect on either peak I or II CSD activities. This difference in sensitivity of the isoenzymes to inhibition by glutamate was used to examine the relative regional distributions and the relative contributions to total activity of the glutamate‐sensitive (peak III CSD, GAD) and glutamate‐insensitive (peaks I and II CSD) isoenzymes. Glutamate‐insensitive CSD activity contributed only part of the total activity in all brain regions tested (ranging from 23% in the superior colliculus to 64% in the pons). However, the specific activity of glutamate‐insensitive CSD was more constant than the total or glutamate‐sensitive specific activities among the brain regions tested. The results indicate that GAD is responsible for a significant proportion of the total CSD activity in porcine brain.

Integrated circuits can be used to construct a compact, relatively inexpensive device which performs the functions of spike amplitude discrimination and digital post-stimulus histogram generation. The logic diagram, detailed schematic, and tnode of operation of such a system is presented and discussed.

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Chromaffin granules, the catecholaminergic storage granules from adrenal chromaffin cells, lysed in 10(-9)-10(-7) M Fe2+. Lysis was accompanied by the production of malondialdehyde which results from lipid peroxidation. Both chromaffin granule lysis and malondialdehyde production were inhibited by the free radical trapping agent butylated hydroxytoluene but not by catalase and/or superoxide dismutase. The results suggest that lysis resulted from a direct transfer of electrons from Fe2+ to a component of the chromaffin granule membrane without the participation of either superoxide or hydrogen peroxide and may have resulted from lipid peroxidation. In some experiments, ascorbate alone induced chromaffin granule lysis which was inhibited by EDTA, EGTA, or deferoxamine. The lysis was probably caused by trace amounts of reducible polyvalent cation. Lysis sometimes occurred when Ca2+ was added with EGTA (10 microM free Ca2+ concentration) and was consistently observed together with malondialdehyde production in the presence of Ca2+, EGTA, and 10 microM Fe2+ (total concentration). The apparent Ca2+ dependency for chromaffin granule lysis and malondialdehyde production was probably caused by a trace reducible polyvalent ion displaced by Ca2+ from EGTA and not by a Ca2+-dependent reaction involving the chromaffin granule.