We evaluated the efficacies of five treatment procedures for eliminating ascorbate interference in the enzymatic determination of urinary oxalate. Aliquots of urine samples, containing different amounts of added ascorbate and oxalate, were individually subjected to ferric chloride, sodium nitrite, sodium periodate, charcoal, or ascorbate oxidase treatment to eliminate ascorbate interference. Oxalate contents of the urine samples were then determined by a banana oxalate oxidase-horseradish peroxidase-linked assay with 3-methyl-2-benzothiazolinone hydrazone and 3-(dimethylamino)benzoic acid as chromogens. Only those urine samples treated with ascorbate oxidase or charcoal consistently gave recovery of oxalate close to 100%. Treatment with other reagents, though improving the recovery of oxalate, gave inconsistent results. On the basis of these data, we describe procedures for simply and reliably assaying oxalate by using banana oxalate oxidase.

Urease enzyme was entrapped in cotton reinforced cellulose triacetat.e fiber and such enzyme fiber bits were then bristled on to plastic coated wire pieces at right angles with a 360' sweep to form minibrushes. These brushes were employed, in place of soluble enzyme, for the conversion of urea to ammonia in clinical samples and the amount of ammonia nitrogen formed was then estimated by Berthelot reaction. The above brush method compares well with that of soluble enzyme analysis in sensitivity, accuracy, reproducibility, recovery and reliability. The enzyme brush is handy to use, 163

Accumulation of oxalate leads to hyperoxaluria and calcium oxalate nephrolithiasis in man. Since oxalate is a metabolic end product in mammals, the feasibility of its enzymic degradation has been tested in vivo in rats by administering exogenous oxalate oxidase. Oxalate oxidase, isolated from banana fruit peels, in its native form was found to be non-active at the physiological pH of the recipient animal. However, its functional viability in the recipient animal was ensured by its prior binding with ethylenemaleic anhydride, thus shifting its pH activity curve towards the alkaline range. Rats implanted with dialysis membrane capsules containing such immobilized oxalate oxidase in their peritoneal cavities effectively metabolized intraperitoneally injected [Yloxalate as well as its precursor [Wlglyoxalate.The implantation of capsules containing coentrapped multienzyme preparations of oxalate oxidase, catalase and peroxidase led to a further degradation of administered [Wloxalate in rats. Oxalate oxidase Nephrolithiasis

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