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Biomedical subjects

T Exner

Publications and source records attributed to T Exner.

At least 55 records · Page 3Linked to original sources
PubMed1989

Coronary artery vasculitis and myocardial infarction associated with antiphospholipid antibodies in a pregnant woman.

A 28-year-old, 16 week primigravida presented with an acute anteroseptal myocardial infarction and a past history of recurrent venous thromboembolism and primary infertility. Although she lacked other clinical features of systemic lupus erythematosus, she had a circulating 'lupus' anticoagulant, anticardiolipin antibodies, a weakly positive anti-nuclear antibody and thrombocytopenia. She died suddenly despite corticosteroid therapy and autopsy revealed coronary arteritis and thrombosis.

Adult↗
PubMed1988

Separation of anticardiolipin antibodies from lupus anticoagulant on a phospholipid-coated polystyrene column.

We describe two novel developments. The first is the preparation of a "cemented" chromatography column comprising siliconized sand-coated by and cemented together with polystyrene thus providing a large hydrophobic surface area suitable for passive antigen absorption. The second is the coating of such a matrix with phospholipid and its use for separating anticardiolipin antibodies from lupus anticoagulant activity in the plasma of a patient with the lupus obstetric syndrome. This is the first description of the separate identities of these two antibodies.

Antibodies↗
PubMed1988

Characterisation and some properties of the protein C activator from Agkistrodon Contortrix Contortrix venom.

The protein C activator (PCA) detectable in the venom of Agkistrodon Contortrix Contortrix (ACCV, Southern Copperhead) by specific immunochromometric assay and anticoagulant activity has been isolated and partially characterized. Chromatography of the crude venom on SP-Sephadex followed by Con A Sepharose and finally on hydroxylapatite was necessary to achieve an electrophoretically - pure product. The isolated PCA is a single chain glycoprotein with strong positive charge and an apparent molecular weight of 36,000. It had an immediate-inhibiting effect on the activated partial thromboplastin time (APTT) of normal plasma with no noticeable effect on the prothrombin time. Its prolonging effect on the APTT was dependent on protein C and it appeared to interfere with the contact mechanism rather than with factors V and VIII. It had enzymatic activity on some tripeptide chromogenic substrates sensitive to thrombin and kallikrein. When mixed with normal plasma it generated activity on substrates sensitive to activated protein C and should be useful for studies of protein C.

Animals↗
PubMed1988

Cell responses to biomaterials. II: Endothelial cell adhesion and growth on perfluorosulfonic acid.

We report here the use of perfluorosulfonic acid (Nafion) as a substratum for the growth of bovine aortal endothelial cells. This support which can be generated in a number of forms is at least as efficient in maintaining the growth of endothelial and other cell types as tissue culture grade polystyrene (TCP) and represents an advance in this regard over polytetrafluoroethylene (Teflon). The mechanism underlying the different cell attachment capacities of these three polymers is not readily related to their different protein binding patterns. While Nafion adsorbs more total protein from serum than Teflon or TCP, it adsorbs relatively less of the major cell adhesive proteins, vitronectin and fibronectin, than does Teflon. Both Nafion and Teflon had comparable but low thrombogenic potential by in vitro tests. Teflon or expanded Teflon (Gore-tex) coated with a thin film of Nafion assumes the cell supportive characteristics of Nafion and hence the modification of these surfaces by the induction of a stable bond between Teflon (in various forms) and Nafion may provide a composite vascular graft material which has all the desirable qualities of both materials.

Animals↗
PubMed1988

Autoimmune cardiolipin-binding antibodies in oral anticoagulant patients.

In a routine clinic of patients taking regular oral anticoagulant therapy (warfarin, n = 140) 14% were found to have elevated levels (greater than 4 SD above normal) of anticardiolipin antibody (ACA) assessed by a well standardised enzyme linked immunosorbent assay (ELISA). There was a higher incidence of raised ACA in patients being treated for thrombotic episodes (9/47 = 19%) than in cases with heart valve replacements (8/75 = 11%). Furthermore, the highest ACA titres were in younger patients with thromboses scheduled for short-term anticoagulant treatment. Borderline DNA binding studies, together with some positive ANA results, suggested autoimmune etiology in the minority of these cases. Lupus anticoagulant was strongly detectable in only one such patient. The ACA were predominantly IgG (14/17) and did not appear to compromise the conditions of patients while on anticoagulant therapy. Raised ACA may be a highly significant marker for an acquired prothrombotic state.

Administration, Oral↗
PubMed1988

Monitoring lupus anticoagulant-positive pregnancies with umbilical artery flow velocity waveforms.

The presence of the "lupus anticoagulant" in maternal blood is associated with thrombosis in the placental vessels and a high rate of fetal loss. We followed six pregnancies in four mothers positive for lupus anticoagulant autoantibody with Doppler umbilical flow studies. The women were not treated with any drugs, and clinical management was guided by close fetal surveillance including umbilical flow studies. Umbilical artery flow velocity waveforms detect vascular abnormalities in the fetal umbilical placental circulation and were used as an early indicator of developing disease. All pregnancies produced live-born infants. These cases indicate the potential value of such studies in the management of this group at high risk of fetal loss.

Autoantibodies↗
PubMed1987

Fitzgerald factor deficiency in an Australian aborigine.

This case reports the first description of Fitzgerald factor (high molecular weight kininogen) deficiency in Australia. Since this homozygous abnormality was found in an Aborigine it is suggested that the defective gene may be prevalent in some tribes and that abnormal results of clotting tests in Aborigines should be investigated carefully.

Blood Coagulation Disorders↗
PubMed1986

Simple immunochromometric assay for protein C activity.

Protein C binds readily from human plasma to antibody-coated wells, where it may be quantitated with an iodine 125-labeled antibody to protein C. Treatment with thrombin results in a small reduction in the protein C antigen detectable by this immunoradiometric assay (IRMA). However, activated protein C resulting from thrombin treatment and retained by the antibody on a solid phase may be detected by an overnight incubation with chromogenic substrates S-2366 or CBS 34.47. The immunochromometric assay (ICMA, analogous to IRMA) described uses a heterologous antibody to protein C, activation with relatively low concentrations of bovine thrombin, and quantitation by hydrolysis of chromogenic substrate in a convenient 96-well microtiter plate system. The correlation between IRMA and ICMA protein C results was found to be good with normal persons and patients with liver disease. Patients taking oral anticoagulants had reduced protein C antigen (IRMA) but even lower protein C by ICMA, indicating that inactive forms were present.

Animals↗
PubMed1985

Detection of specific proenzyme activators in snake venoms by a new immunoabsorbant-chromogenic substrate method.

In separate experiments, antibodies to plasminogen, factor X and protein C were applied to microtitre trays as commonly used in enzyme-linked immunoassays. After incubation with dilute normal human plasma as a source of the corresponding proenzyme antigen, the wells were exposed to dilutions of various snake venoms. After thorough washing, the microtitre tray wells were tested overnight with chromogenic tripeptide substrates known to be relatively specific for the activated forms of the above factors, i.e., plasmin, factor Xa and activated protein C. The immunochromometric assay described detected two new activators of protein C in Agkistrodon piscivorus and Agkistrodon contortrix venoms and a new factor X activator in Agkistrodon rhodostoma venom. Gel filtration of the latter venom indicated that the factor X activator eluted with high molecular weight, was clearly distinct from the peak fibrinogen clotting activity (Ancrod) and appeared to have no procoagulant activity. Although several Bothrops venoms appeared to contain plasminogen activator by this technique, the observed strong chromogenic activity was observed in microtitre wells independently of plasminogen and represented nonspecific amidase activity.

Enzyme Activation↗
PubMed1985

Similar mechanism of various lupus anticoagulants.

Potent lupus inhibitors from various patients were mixed with platelet free normal plasma and were compared in activated partial thromboplastin time (APTT), dilute prothrombin time (dil. PT), kaolin clotting time (KCT), contact product clotting time (CPCT), and Russell viper venom clotting time (RVVCT) tests. In the last three tests platelets and platelet lipid substitutes were avoided to enhance the sensitivities of these tests for the lupus anticoagulant. Correlations between the KCT and the other tests were mostly good, indicating that different lupus inhibitors functioned by a similar mechanism. There was no significant trend between particular clinical symptoms and individual coagulation test combinations. The KCT was found to be the most sensitive test for the lupus inhibitor, followed by the CPCT, RVVCT, dil. PT and APTT tests. Activated platelets tended to correct the APTT lupus inhibitor defect in all except the strongest inhibitor cases.

Blood Coagulation Disorders↗
PubMed1985

Some studies with a monoclonal antibody directed against human fibrinogen.

Some properties of a monoclonal antibody generated against the fibrinogen component of a factor VIII preparation were investigated. The antibody bound with equal affinity in solid phase radioimmunoassays to fibrinogens isolated from both normal patients and patients with von Willebrand disease. It reacted in a sensitive immunoassay of plasma fibrinogen. The specificity of the antibody was confined to the parent molecule with no significant inhibition of fibrinogen binding by the fibrinogen degradation products (FDPs) X, Y, D, or E. The antibody had no significant effect on the activated partial thromboplastin time and prothrombin time of normal plasma. However, it prolonged the thrombin time as determined by the Clauss chronometric fibrinogen method. During fibrinogen lysis by plasmin immunoreactivity of fibrinogen to the antibody was lost at the same rate as the clottable fibrinogen content determined by the Clauss assay. The lack of reactivity of the antibody with FDPs makes it a suitable reagent for investigating plasmin activity as well as studying fibrinogen and fibrin. These findings suggest that the epitope of the antibody lies within the polar protruberance of the carboxy terminal end of the A alpha chain of fibrinogen and is destroyed by plasmin cleavage.

Antibodies, Monoclonal↗
PubMed1985

Multiple cerebral thrombosis in Fletcher factor (prekallikrein) deficiency: a case report.

Despite markedly prolonged activated partial thromboplastin times (APTT) patients with Fletcher factor (prekallikrein) deficiency do not clinically bleed. However, there is one reported case of myocardial infarction associated with prekallikrein deficiency. These clinical observations suggest that the contact mechanism has a minor role in normal in vivo hemostatic function. We report a further two cases of prekallikrein deficiency in Caucasian siblings. The propositus presented with multiple cerebral thrombosis. Cautious anticoagulation resulted in massive cerebral hemorrhage and death of this patient. The sibling was investigated in an attempt to establish a possible defective fibrinolytic pathway in vivo. New sensitive tests for fibrinolysis were used. These included radioimmunoassay of fibrin degradation product "D," B beta 15-42, and in vitro 125I-labelled fibrin lysis assays. The plasma half-life of prekallikrein in this patient was calculated to be 58 hr. Family studies of heterozygotes were also performed. Prekallikrein deficiency is found not to be important in normal in vivo fibrinolysis, which possibly operates via tissue or vessel wall fibrinolytic activator release.

Adolescent↗
PubMed1985

Comparison of two simple tests for the lupus anticoagulant.

Mixtures of various patient lupus inhibitor-containing plasmas and normal plasma were tested concurrently with the dilute tissue thromboplastin inhibition (DTTI) test and the kaolin clotting time (KCT). The KCT was found to be more sensitive to the presence of the lupus inhibitor than the DTTI. The principle of reducing the platelet phospholipid content in the KCT test plasma to enhance sensitivity for the lupus inhibitor was extended by using plasmas filtered through 0.22-micron cellulose acetate filters.

Blood Coagulation Factors↗
PubMed1985

Monoclonal antibodies to human FVIIIR:Ag and FVIIIC.

A series of monoclonal antibodies have been produced which recognize different epitopes of the factor VIII molecule. The antibodies were raised in mice against high purity factor VIII (FVIII) and the mouse spleens used in cell fusion experiments. Following cell fusion the hybridoma supernatants were used for screening with a solid phase radioimmunoassay (RIA) technique. The antibodies detected were differentiated by their degree of attachment to 2 components of the FVIII molecule, FVIII related antigen (FVIIIR:Ag) (also called von Willebrand's Factor) and FVIII coagulant (FVIIIC). Immunofluorescence and immunoperoxidase studies both showed the FVIIIR:Ag antibodies to be localized to the endothelial cells of the blood vessel walls. They can, therefore, be used for histological identification of these cells on cryostat and paraffin sections. The anti-FVIIIR:Ag antibodies have no anticoagulant properties, whereas the anti-FVIIIC antibody reacts as an instant inhibitor with a strength of 35,000 new Oxford U/ml. These antibodies are stable reagents and suitable for radioimmunoassay for both FVIIIR:Ag and FVIIIC.

Animals↗
PubMed1984

Fibrinogen Adelaide: a familial hypodysfibrinogenaemia associated with abnormal alpha chains.

A familial hypodysfibrinogenaemia occurring in four females with occasional haemorrhagic problems in an Adelaide family was investigated. Affected family members had slightly prolonged thrombin time, prothrombin time and Reptilase time tests, and apparently elevated levels of fibrin degradation products (FDPs). Fibrinogen assessed by reactivity with thrombin (Clauss method) was significantly less than fibrinogen determined by various other methods, though even by immunoquantitation fibrinogen levels were only slightly above half normal in affected family members. Isoelectric focussing (IEF) of the reduced patient's fibrinogen in urea/polyacrylamide gel revealed minor components with higher isoelectric points (pI) than present in normal fibrinogen or fibrin. These were shown to have a molecular weight similar to the alpha chain of fibrin by subsequent sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The abnormal species tended to remain in plasma after clotting with Reptilase or thrombin although polymerization of the clotted fibrin was normal. The magnitude of the pI shift relative to normal fibrin alpha chain indicated an increased positive charge on the abnormal species.

Adult↗