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Biomedical subjects

W H Seegers

Publications and source records attributed to W H Seegers.

At least 19 recordsLinked to original sources
PubMed1978

Effects of autoprothrombin II-A on epinephrine-induced platelet aggregation of normal- and coumadin-treated dogs.

Platelet-rich plasma from dogs and from coumadin-treated dogs aggregated at the same optimum concentration of epinephrine. Neither protein C nor its active form called autoprothrombin II-A was necessary for aggregation of dog platelets with epinephrine. For platelet aggregation, suboptimal concentrations of epinephrine were potentiated by addition of purified autoprothrombin II-A. The latter, by itself, induced platelet aggregation in high concentration.

Animals↗
PubMed1978

Antithrombin III. Theory and clinical applications. H. P. Smith Memorial Lecture.

Antithrombin III is one of the main inhibitors in the blood coagulation mechanisms. Thrombin and factor Xa are slowly inactivated by it, as well as other serine proteinases of the coagulation mechanisms. Heparin tremendously accelerates the inhibitory function of antithrombin III. In the process antithrombin III activity is also reduced. Heparin retards the thrombin-fibrinogen reaction, but otherwise the effectiveness of heparin as an anticoagulant depends on antithrombin III in laboratory experiments, as well as in therapeutics. The activation of prothrombin is inhibited, and any thrombin or other vulnerable protease that might generate becomes inactivated. The measurement of antithrombin III concentration in blood is now achieved by research methods, as well as by methods that are practical for routine use. The tests require either thrombin or factor Xa as substrate, and could be specific for antithrombin III. There are congenital as well as acquired deficiencies of antithrombin III. The inhibitor is also found in tissues.

Antithrombins↗
PubMed1977

Amino acid sequence of human prothrombin fragments 1 and 2.

The amino acid sequence of the nonthrombin half of human prothrombin is presented. Prothrombin fragment 1 has 155 amino acid residues as compared with 156 for the bovine equivalent. Ten gamma-carboxyglutamic acid residues are at the same location in each species. Human prothrombin fragment 2 contains 118 amino acid residues, as does the similar bovine fragment. Comparing bovine and human prothrombin fragment 1 we found 131 residues to be identical (84%). In prothrombin fragment 2, 84 residues were identical (71%). Assuming a time span of 90 million years since the radiation of several orders of placental mammals, prothrombin fragments 1 and 2 incorporated one substitution site per 100 amino acid sites every 11.2 and 6.3 million years, respectively. Internal homology is acribed to partial gene duplication, with the most likely crossover point located between residues 60-61 and residues 165-166.

Amino Acid Sequence↗
PubMed1977

Autoprothrombin ii-a, thrombin, and epinephrine: interrelated effects on platelet aggregation.

Platelets aggregate with thrombin-free autoprothrombin II-A. Aggregation was dependent on an intact release mechanism since inhibition of aggregation occurred with adenosine, colchicine, or EDTA. Autoprothrombin II-A reduced the sensitivity of platelets to aggregate with thrombin, but enhanced epinephrine-mediated aggregation. Autoprothrombin II-A directly competes for membrane sites sensitive to thrombin. It allows complexes to from with epinephrine. There was no absolute requirement for autoprothrombin II-A since epinephrine aggregated dog platelets at the identical optimum concentration following Coumadin treatment.

Animals↗
PubMed1977

Usefulness of new analytical reagents demonstrated with coumadin-modified plasma.

Prothrombin, factor X or factor IX were removed specifically from bovine plasma by immunological techniques. Each depleted plasma is responsive to the respective purified component, and was used to follow the blood changes produced in a steer's blood by Coumadin administration. A factor IX-VII reagent was also used to follow changes in factor IX and factor VII activity. It is suggested that the new reagents may have practical value for qualitative and quantitative work in blood coagulation studies.

Animals↗
PubMed1976

Improved procedures for the purification of selected vitamin K-dependent proteins.

Improved methods are described to obtain bovine prothrombin, Factor IX, Protein C, and autoprothrombin III (Factor X, Auto-III) in purified form. The prothrombin had a specific activity of 4,340 Iowa units/mg. Theoretically, a preparation of clean thrombin should have a specific activity of 8,200 U/mg, because 47.08% of the protein in prothrombin is lost when thrombin forms. Such thrombin preparations have been obtained (Arch. Biochem. Biophys. 121, 372 (1967)). The prothrombin concentration of bovine plasma is near 60 mg/liter. Protein C, first isolated by Stenflo (J. Biol. Chem. 251, 355 (1976)), was found to be the precursor of autoprothrombin II-A (Auto-II-A), discovered earlier (Thromb. Diath. Haemorrh. 5, 218 (1960)). Protein C (Factor XIV) was converted to Auto-II-A (Factor XIVa) by thrombin. Digesting purified Auto-III with purified thrombin removed a small glycopeptide from the COOH-terminal end of the heavy chain to yield Auto-IIIm. Auto-III thrombin leads to Auto-IIIm + peptide. Auto-IIIm was not converted to the active enzyme with thromboplastin, and furthermore, inhibited the activation of purified native Auto-III with thromboplastin. Auto-IIIm was also not converted to the active enzymes when the procoagulants consisted of purified Factor VIII, purified Factor IXa, platelet factor 3 and calcium ions. The "activation peptide" released by RVV-X from the NH2-terminal end of the heavy chain and the active enzyme (Auto-Cm) were purified. Auto-III was also activated with purified RVV-X. The same "actid of Auto-Cm. Purified Factor IX developed anticoagulant activity when reacted with an optimum concentration of purified thrombin. A suitable reagent for the assay of Factor IX was prepared by removing prothrombin complex from anticoagulated bovine plasma and restoring the prothrombin and Auto-III concentration with use of the respective purified proenzymes.

Animals↗