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Biomedical subjects

O R Odegård

Publications and source records attributed to O R Odegård.

15 recordsLinked to original sources
PubMed1979

Diagnostic problems in thromboembolism.

Some pathogenetic aspects and diagnostic problems in venous thrombosis are briefly discussed. Emphasis is put on the value of blood tests. It is concluded that the various tests are neither able to detect ongoing thrombosis, nor to identify a prethrombotic state. The necessity of direct demonstration of the thrombus preferably by phlebography is stressed. The tests are valuable as a part of the "coagulation profile", and may aid to discover e.g. antithrombin III deficiency or subnormal fibrinolytic activity.

Antigen-Antibody Complex↗
PubMed1978

On use of chromogenic substrates for studies of coagulation inhibitors.

Methodological problems encountered using chromogenic substrates on thrombin and Xa are discussed: (1) influence of substrate on inhibitor; (2) influence of heparin; (3) optimal concentrations; (4) specificity; (5) denatured enzymes, and (6) natural versus chromogenic substrates.

Antithrombins↗
PubMed1978

Antithrombin III: critical review of assay methods. Significance of variations in health and disease.

Thrombin or factor Xa added to plasma are inactivated by antithrombin III (At-III). The inactivation is accelerated by heparin, permitting assay systems which rapidly measure the At-III content of diluted plasma. Without heparin, the slow inactivation rates may be measured. Existing activity assays (fibrinogen or chromogenic substrates) and immunoassays of At-III have been reviewed. Correlation studies show a close correlation between the results of immunoassay and the results of most activity assays. In health, a narrow range of At-III has been found. The level is low in infancy. Fertile women have on the average somewhat lower levels than men. In old age, the level tends to drop. In clinical material studied with amidolytic assays, subnormal At-III levels were found in hereditary deficiency, liver disease, disseminated intravascular coagulation and in some cases with acute thrombosis. The amidolytic assays are rapid to perform, do not require experience in clotting technique and seem preferable in clinical routine work.

Acute Disease↗
PubMed1978

Automated antithrombin III assay with a centrifugal analyser.

The factor Xa inactivating function of antithrombin III is measured automatically by an amidolytic method, adapted to a centrifugal analyser. Plasma is diluted in buffer with heparin. In stage I, diluted plasma is incubated with excess factor Xa. Heparin accelerates the saturation of antithrombin with factor Xa. In stage II, remaining factor Xa is determined with the chromogenic substrate Bz-Ile-Glu-Gly-Arg-pNA. The precision of the present assay compares favourably with that of the clotting assays and immunoassay. There is a close correlation (r = 0.82) between the results obtained with this assay and the immunoassay of antithrombin III.

Absorption↗
PubMed1977

Antifactor Xa activity in thrombophilia. Studies in a family with Ar-III deficiency.

Antithrombin III (At-III) concentration and amidolytic assays reflecting functions of the At-III molecule were studied in members of a family with a strong tendency to thrombosis. Antifactor Xa and heparin cofactor activity closely parallel at At-III concentration. In all individuals with a history of thrombosis At-III concentration was about 50% of normal. The clinical features and causes of death are briefly reviewed. Mean age in deceased family members with a tendency to thrombosis was 55 years, in members with no history of thrombosis it was 65 years.

Adult↗
PubMed1976

A simple amidolytic method for the determination of functional active antithrombin III.

A simple amidolytic method for the determination of the concentration of functionally active antithrombin III is described. Plasma is diluted with buffer containing EDTA and Polybrene. In stage I, diluted plasma is incubated with thrombin. EDTA retards fibrin polymerization, and plasma fibrinogen does not influence the assay. Polybrene makes the assay result independent of heparin. In stage II, remaining thrombin is determined with the chromogenic substrate benzoyl-Phe-Arg-p-NA. The method is simpler and has a higher accuracy than clotting methods. There is a close correlation between the results obtained with this assay and with immunoassay of antithrombin III.

Antithrombins↗
PubMed1976

Antifactor Xa activity measured with amidolytic methods.

Methods for the assay of antifactor Xa activity in the presence and absence of heparin are described. Diluted plasma is incubated with bovine, activated factor X (Xa) in stage I, and remaining Xa is measured with the chromogene substrate Bz-Ile-Glu-Gly-Arg-pNA in stage II. In the presence of heparin, the inactivation is completed in 30 sec, and this method measures total Xa-inactivating capacity in diluted plasma (Method I). In a clincal material, this capacity showed a strong positive correlation (r=0.85) to the thrombin-inactivating capacity of diluted heparinized plasma (heparin cofactor activity) and apparently reflects antithrombin III (At-III) concentration. In the absence of heparin, the inactivation of factor xa occurs slowly. With an incubation of 5 min, about 25% of Xa is inactivated, and this assay reflects initial inactivation of Xa (Method II). With this method, a positive, but less strong correlation to the thrombin-inactivating capacity was found (r=0.58), indicating that inhibitors different from At-III accounts for a minor part of the initial inactivation. Determinations in plasma, in which At-III was removed by immunoadsorption, indicated that At-III accounts for about 80% of the initial inactivation. The results of the assays are not significantly influenced by varying concentrations of fibrinogen, fibrinogen degradation products or heparin in the test plasma.

Amides↗