Multi-centre study of a new CEA enzyme immunoassay using monoclonal antibodies.

The use of a new monoclonal enzyme immunoassay (EIA) for the carcinoembryonic antigen (CEA) (Enzymun-Test CEA) was evaluated in a multi-centre study. Fifteen different laboratories [participated in the study. Data from the investigation were analysed in terms of precision, sensitivity, specificity and correlation with other test methods. The intra-assay coefficient of variation was between 1.3% at 23.0 microg/l CEA and 13.9% at 1.3 microg/l CEA. Inter-assay reproducibility ranged from 3.6% to 19.2%. The apparent sensitivity of the new EIA for CEA was approx. 0.5 microg/l CEA. The findings indicate that lipaemic and haemolytic sera and samples taken from icteric, rheumatic and dialysis patients did not have any influence on the results. There was no evidence that drugs commonly used in the treatment of carcinoma patients have any influence on the assay results. A good correlation between the new EIA for CEA and six other CEA enzyme immunoassay or radioimmunoassay methods was registered. These results seem to be of significance in particular for the monitoring of therapy for carcinoma patients. The new EIA for CEA exhibits a high degree of sensitivity, specificity and reproducibility.

A new approach to photometry of glycated hemoglobin in human blood.

This new approach to measurement of glycated hemoglobin (Hb A1) is a three-step procedure involving (a) conversion of oxyhemoglobin into NO-hemoglobin by sodium dithionite and sodium nitrite in the presence of inositol hexaphosphate; (b) incubation with haptoglobin, which preferentially binds glycated hemoglobin; and (c) determination of the hemoglobin/haptoglobin complex by its peroxidase activity in acid buffer. The procedure is suitable for automated analysis with instruments that are capable of adding a starting reagent. We describe preliminary adaptations for the Abbott VP and Hitachi 705 analyzers and demonstrate the correlation of results with Hb A1 concentrations determined by ion-exchange chromatography.

Kinetic enzymic method for automated determination of total cholesterol in serum.

We describe a rapid, kinetic, fixed-time method for determining serum total cholesterol by use of cholesterol esterase, cholesterol oxidase, and the indicator reaction with peroxidase, 4-aminophenazone, and phenol. On addition of the competitive inhibitor 3,4-dichlorophenol the Michaelis constant of cholesterol oxidase is apparently increased, which extends the linear relation between absorbance change and cholesterol concentration to 20.7 to 25.9 mmol/L, depending on the analyzer being used. For calibration, a single standard is used. Total analysis time is in the range of 80 to 210 s. Incubation temperature is 25 degrees C or 37 degrees C. The single-reagent procedure has been adapted to three different centrifugal analyzers and to the Eppendorf ACP 5040 analyzer. It yields precise and accurate results and is insensitive to potential interferences.

Kinetic determination of serum glucose by use of the hexokinase/glucose-6-phosphate dehydrogenase method.

We have developed a kinetic fixed-time approach for the quantitative determination of serum glucose by use of the hexokinase/glucose-6-phosphate dehydrogenase method. To achieve a large measuring range, we have apparently increased the Michaelis constant of glucose-6-phosphate dehydrogenase through addition of the competitive inhibitor ATP. By this means, serum samples with glucose concentrations up to 55.5 mmol/l could be analyzed without pre-dilution. The method has been adapted to the ENI GEMSAEC analyzer and to the LKB 2086 Mark II analyzer. It yielded satisfactory results with regard to precision. A comparison of the kinetic procedure with the manual end-point method showed good agreement. No interferences from hemoglobin, bilirubin, or lipemia have been observed.

[On the preparation of intermediates in cobyrinic acid biosynthesis by suspensions of Propionibacterium shermanii (author's transl)]. / Zur Cobyrinäure-Biosynthese. Gewinnung von Zwischenprodukten der Cobyrinsäure-Biosynthese mit Zellsuspensionen von Propionibacterium shermanii.

The preparation of a dimethyltetrahtdrouroporphyrin (Faktor II or sirohydrochlorin) using suspensions of Propionibacterium shermanii as well as a promising method for the isolation of tetrapyrrols with at least four carboxy substituents from cell-free extracts and growth media are described. Also a Faktor II-analogue with three methyl groups which are derived from L-methionine is reported. Incorporation experiments indicate that this is an intermediate in cobyrinic acid formation. Because of this, and from spectroscopic (field desorptionmass, visible absorption) studies it is concluded that the "extra" methyl group is located at the meso-carbon between two methylated reduced rings.

[On cobyrinic acid biosynthesis. Novel methylated hydroporphyrins and their role in cobyrinis acid formation (author's transl)]. / Zur Cobyrinsäure-Biosynthese. Neuartige, methylierte Hydroporphyrine und deren Bedeutung bei der Cobyrinsäure-Bildung

Clostridium tetanomorphum and Propionibacterium shermanii were examined for intermediates in the synthetic pathway uroporphyrinogen III leads to cobyrinic acid. The isolation of two novel methylated hydroporphyrins, whose methyl groups are derived from S-adenosyl-L-methionine, is described. Spectroscopic (field desorption-mass, visible absorption) und electrophoretic studies as well as incorporation of labelled substrates indicate that they are analogues of a dihyrouroporphyrin and a tetrahydrouroporphyrin with adjacent reduced rings. Field desorption spectra of the [C2H3]- and [CH3]-tetrahydrouroporphyrin analogues show that the compound contains two methyl groups; it is concluded that the chlorine-like compound has one methyl group. Dehydrogenation experiments indicate that the methyl groups are located at one beta-carbon of the reduced rings. Incorporation experiments suggest that the tetrahydrouroporphyrin-like compound is an intermediate in cobyrinic acid biosynthesis. Studies on the utilization of a heptacarboxyporphyrinogen from C. tetanomorphum for cobyrinic acid formation are also described.