This assay of plasma lipoperoxides involves hydrolysis in dilute H3PO4 at 100 degrees C; complexation of malondialdehyde (MDA), a hydrolysis product, with thiobarbituric acid (TBA); methanol precipitation of plasma proteins; fractionation of the protein-free extract on a C18 column; and spectrophotometric quantification of the MDA-TBA adduct at 532 nm. The detection limit was 0.15 mumol of MDA per liter of plasma. Run-to-run precision (CV) averaged 8 to 13%. Analytical recovery of MDA after addition of tetraethoxypropane standards to 21 specimens of human or rat plasma averaged 98% (SD 7%). Lipoperoxide concentrations (as MDA) averaged 0.60 (SD 0.13) mumol/L in plasma specimens from 41 healthy persons and 1.4 (SD 0.3) mumol/L in plasma specimens from 12 control rats. Mean lipoperoxide concentrations were 1.5 to 2.3 times as great in plasma sampled from rats one to three days after subcutaneous administration of NiCl2 at dosages (250 to 750 mumol per kilogram body wt) previously shown to induce lipid peroxidation in lung, liver, and kidney.

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L-Asparaginase isolated from the BCG strain of Mycobacterium bovis has been purified approximately 100-fold by negative adsorption on Ca-phosphate gel, batchwise adsorption and column chromatography on DEAE-Sephadex, gel filtration through Bio Gel P-200, and crystallization.The final enzyme preparation appeared to be pure on the basis of cellulose acetate and polyacrylamide gel electrophoresis, immunodiffusion, and immunoelectrophoresis in agar gel.Inhibition by crystalline BCG L-asparaginase of blast cell transformation was demonstrated by means of thymidine-3H incorporation in phytohemagglutinin-stimulated rabbit spleen cell cultures. This effect was not observed with heat-inactivated enzyme.Antibody synthesis in spleen cell cultures which were secondarily stimulated in vitro with polio virus was also depressed.Intradermal inoculation of crystalline BCG L-asparaginase in BCG-sensitized guinea pigs gave no significant tuberculin type reaction.

A procedure for the purification of an ornithine carbamoylphosphate transferase isolated from a Staphylococcus aureus strain is reported. The procedure consists of the following steps: water extraction of the crude enzyme by autolysis under a toluene layer of the acetone dried bacteria cells, lyophilization of the crude extract, molecular sieving chromatography on a Bio Gel P‐150 column and as a final step the electrophoresis on Sephadex G‐200 plates. A 100‐fold purification with a 50% yield is realized. The purified preparation so obtained appeared to be pure on the basis of acrylamide gel electrophoresis, thin layer chromatography, immunodiffusion and immunoelectrophoresis. The apparent molecular weight of the enzyme as determined by molecular sieve chromatography is 200 000 ± 30 000. The Km value for l‐ornithine as substrate is 3 mM and for carbamoylphosphate 0.7 mM. Arrhenius activation energy is 13 775 cal/mol. NH2‐terminal amino acid is glycine: COOH‐terminal amino acid is glutamic acid. Two unmasked SH‐groups and two S‐S interchain bridges per molecule were found.

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