[Preparation of water-soluble hydronaphthoquinone derivatives and its application to the determination of hydrogen peroxide in clinical chemistry]

Several 1-alkoxy-2,3-dichloro-4-hydroxynaphthalene derivatives were prepared. These compounds were oxidized by hydrogen peroxide in the presence of a peroxidase to give 2,3-dichloro-1,4-naphthoquinone, which then reacted with various alkyl benzoylacetates to develop blue coloration with absorption maximum at greater than 600 nm. The color development reaction can be applied to the determination of appropriate serum constituents such as cholesterol.

A homogeneous assay system of aspartate aminotransferase iso-enzymes using proteases and application for clinical evaluation of myocardial infarction

We designed a rapid, homogeneous assay for human aspartate aminotransferase (AST) isoenzymes, by a selective proteolysis of soluble AST (s-AST), using chymotrypsin and protease 401. The linearity of mitochondrial (m-AST) was elongated up to 4000 U/l. m-AST values from the human liver, and determined by a homogeneous assay using protease 401 or chymotrypsin, were relative to those obtained using an immunoprecipitation method. In perioperative patients or those with an acute myocardial infarction, the peaks of s-AST and m-AST values were noted 13 h and at 57 h after ictus, respectively, whereas the peak of ratio between was seen 6 h after ictus. In the case of Budd-Chiari syndrome, the maximum levels of the two AST activities were evident 14 days after hospitalization and the peak of ratio between them was seen after 7 days. We propose that this homogeneous assay can serve as a diagnostic tool for early phase detection of myocardial infarction and of Budd-Chiari syndrome.

Antithrombin-III assay without influence of heparin cofactor II

A new biological method for the assay of plasma antithrombin-III (AT-III) activity was developed without influence from heparin cofactor II (HC-II). AT-III deficient plasma is used as a substrate and diluted prothrombin time reagent as a reaction trigger for the specific assay of AT-III. The AT-III deficient plasma is prepared by passage of plasma through a heparin-agarose column. In the presence of heparin, AT-III in the sample shows concentration dependent anticoagulant activity and calibration curve is linear on semi-logarithmic graph paper. The results of reproducibility, recoveries and correlation studies with a chromogenic assay indicate that this biological method is reliable and suitable for routine use in clinical laboratories. Influence of HC-II is minimal. The method provides several advantages over those of chromogenic substrate and fibrinogen.

A new enzymatic method for determination of serum choline-containing phospholipids

A new enzymatic method is presented for the determination of serum choline-containing phospholipids with a combined enzymatic method using phospholipase D (from Streptomyces species), choline oxidase (from Arthrobacter species) and peroxidase. The method is reproducible, and the results correlate well with those obtained by the conventional digestion method (Hoeflmayr, J. and Fried, R. (1966) Med. Ernaehr. 7, 9-10). The method affords better specificity, requires a smaller quantity of the sample and shorter time than those previously reported, and has excellent precision.