The mechanism of interference of bilirubin on the peroxidase reaction systems is discussed from spectrophotometric and kinetic findings.
1. In the oxidative coupling reaction system with 4-aminoantipyrine and phenol, bilirubin reacted with the phenol intermediate produced by peroxidase reaction. Then, bilirubin interfered on the peroxidase reaction according to a competitive inhibition against the same acceptor for the phenol intermediate, 4-aminoantipyrine.
2. Bilirubin, also, interfered on the peroxidase reaction as a hydrogen donor of peroxidase and this interference resulted in a competitive inhibition to the same hydrogen donor such as phenol, ABTS, o-dianisidine. Increasing the concentrations of the hydrogen donors, rger Ki values were obtained.
3. The interference of bilirubin was partialy dependent on the measuring wavelength. Setting the measuring wavelength longer than 520nm, the apparent interference of bilirubin was reduced by the production of biliverdin or another unknown complex with the phenol intermediate.

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A new substrate, o-toluoylcholine, was synthesized for the estimation of serum cholinesterase activity. It was specific for pseudo-cholinesterase activity and was stable for storage in cold after dissolving in buffer and against temperature and pH. Serum cholinesterase activity was also able to be estimated by the reaction rate assay using o-toluoylcholine as asubstrate.
o-Toluoylcholine was slightly hydrolyzed by α-amylase, cholesterol esterase and trypsin from the pancreas, as well as by carboxylesterase from the liver.
Good correlation was observed between this enzymatic metho dusing o-toluoylcholine as a substrate and the ΔpH method using acetylcholine as a substrate.

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A new method is described for determining the concerltration of creatinine (and also of creatine) in human serum. The method consists of enzymatic conversion of creatinine to formaldehyde via creatine and sarcosine.
The first enzyme involved is creatinine amidohydrolase (creatininase) which reversively converts creatinine to creatine. The second enzyme is creatine amidinohydrolsae (creatinase) that gives sarcosine from creatine, the third enzyme being sarcosine dehydrogenase by whic sarcosine is converted to glycine and formaldehyde. The formaldehyde produced is determined by measuring the color intensity of red purple tetrazine caused by the reaction of HCHO with AHMT (4-amino-3-hydrazino-1, 2, 4-triazole) in the presence of KlO₄ at alkaline region. Only a 0.1ml of serum is enough to measure the conterlt of creatinirle, and deproteinization proCedure is unnecessary. Linear relationship was observed between the intensity of absorbance and the concentration of creatinine. The comparison of the results obtained by the Folin method with those by the present one gave a value of 0.992 as the correlation coefficient (r).

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we have developed a new method to measure β₂-microglobulin by a tungsten lamp nephelometer.
This method has some special merits such as a short measuring time, simple assay procedure, good reproducibility and good correlation with the radioimmunoassay method.
Because of its low cost and simplified procedure, we believe this method will find increased acceptance as the field for the clinical application ofβ2-microglobulin widens

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An enzymatic determination of serum creatinine using creatinine deiminase (EC 3.5.4.-) and glutamatedehydrogenase (EC 1.4.1.2) is described. The principle of this method is as follows;creatinine is degradated by creatinine deiminase to produce ammonia and N-methylhydantoin, and the ammonia produced is coupled with glutamate dehydrogenase. The change in absorbance at 340nm is mesured.
The correlation coefflcient between the present method and Folin method was 0.997 and regression line was y=1.0x-0.26 (y=present method In this method). serum creatinine is determined without deproteinization.

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Newborn rats were inoculated with a fibrosarcoma cell line derived from spontaneously transformed fetal lung cells in culture. Tumor-bearing rats were sacrificed at several stages of tumor growth along with age-matched normal controls. Assays were carried out on liver and tumor tissue for the following: glucosamine-6-P synthetase (Lglutamine: D-fructose 6-P aminotransferase, EC 2.6.1.16.), UDP-GlcNAc 2'-epimerase (UDPN-acetylglucosamine 2'-epimerase, EC 5.1.3.-).
Specific activities of glucosamine-6-P synthetase and UDP-GlcNAc 2'-epimerase were signiflcantry increased in the livers of tumor-bearing rats. The increase in specific activities of the two hepatic enzymes were found to be correlated with tumor size. Tumor tissue had an equivalent glucosamine-6-P synthetase specific activity to normal liver, while UDP-GlCNAc 2'-epimerase activity was 18% that found in normal liver. Seromucoid concentration increased with the growth of the tumor.

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A calculation method was described for the estimation of the normal range of laboratory tests from patients data in the clinical laboratory. Two calculation procedues were applied for the normal range estimation. Logarithm of histogram frequencies are plotted against measured variable, and the central portion of this histogram was fitted to the 2nd order regression curve using the least square method. The regression curve corresponds theoretically to the normal distribution curve, and the lower and the upper limits of the normal range were calculated from the parameters of the normal distribution curve (L-method). The other method is that logarithm of histogram frequencies are plotted against logarithm of measured variables and the 2nd order regression curve fitted to this histogram corresponds theoretically to the log-normal distribution curve (LL-method). The upper and the lower limits were estimated from the parameters of the distribution curve These calculation methods are applied to several model distributions and to clinical laboratory data, and accuracy and precision of the calculation methods are checked. After general evaluation of the methods, it was concluded that LL-method can be used for the estimation of the lower limit of the normal range, and that L-method can be used for the estimation of the upper limit.

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The method described allows a relatively rapid and sensitive assay of lipase activity in serum by the use of olive oil as a substrate. We have modified the photometric, copper soap method for determining fatty acids described by Maehata and Naka (Jap. J. Clin. Chem., 1, 447 (1972)). The free fatty acids are separated in the form of their copper salts by chloroform-heptane extraction and organic layer is obtained as a supernatant by centrifugation. Copper is determined by colorimetry with 2-(2-thiazolylazo)-p-cresol. Centrifugal procedure is carried out lust once differing from other colorimetric method.
The site of the action of lipase is the interface between the oil drops and the aqueousphase, so that the degree of emulsification plays an important part in establishing the active substrate concentration. Therefore, Preparation of substrate emulsion, such as pH, kind of buffer, olive oil concentration, arabic gum concentration, and mixing condition, has to be made most carefully.
The precision of the method was satisfactory and the relationship between this assay and Cherry-Crandall 3-hour method was close. The method is suitable for estimating lipase activity in a Clinical laboratory

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A simple, precise and sensitive method for separation and determination of free and conjugated bile acids in human serum without prior hydrolysis is described. The free, glycine-and taurine-conjugated bile acids are separated into groups by ion-exchange chromatography on a newly developed lipophilic gel, piperidinohydroxypropyl Sephadex LH-20. Bile acids in each group are determined by the enzymatic method using 3x-hydroxy. steroid oxidoreductase. The proposed assay system is applicable to simultaneous quantitation of free and conjugated bile acids with satisfactory precision. The serum bile acid levels were estimated on some patients with hepatobiliary diseases.

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A new fluorometric method for determination of the activity of urinary dipe-ptidyl-aminopeptidase IV (X-prolyl dipeptidyl-aminopeptidase) was applied to the assay of the enzyme in the urine from patients with renal diseases. It was possible to use urine from patients directly without any preliminary isolation procedures. The urinary enzyme activity was found to be elevated in some patients with chronic glomerulonephritis and nephrotic syndrom.

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Determination of total protein in cerebrospinal fluid using electron spin resonance is described. As signal intensity of ESR is decreased by addition of protein to spin labeled compound, a good standard curve is obtained using human serum (or control serum), which is similar to cerebrospinal fluid in composition.
Sample volume used in this method is only 100μl, and the comparison of values with Esbach method has also been performed, but the values by present method was higher than that of Esbach method in like result of high values by biuret method.

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It has been well known that cephalosporins derivatives interferes with the nitroprusside reaction which is applied for detection of acetone. In order to measure acetone semiquantitatively in urinary samples containing these interfering materials, we deviced a simple apparatus. of which principle was as follows: a cotton boll being suspended from the top of a glass tube captured vaporized acetone which was arisen from urine laid on the bottom of the tube by boiling it and the content of acetone in the cotton boll was measured using a testing stick.
The validity of this method was tested using 33 urinary samples which contained acetone as well as the cephabsporin derivatives. The method was revealed to be satisfactory for a clinical use.

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