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G D Wilner

Publications and source records attributed to G D Wilner.

At least 55 records · Page 3Linked to original sources
PubMed1978

Molecular basis for measurement of circulating fibrinogen derivatives.

Fibrinogen plays a pivotal role in both the humoral and cellular mechanisms involved in hemostasis. In performing its hemostatic function, fibrinogen in turn is acted on by several independent enzyme systems that either modify its structure or cleave specific fragments of the molecule into the surrounding milieu. Measurements of enzymatically modified fibrinogen or its proteolysis products represent a means whereby the action of these specific enzymes can be quantitated both in vitro and in vivo. Advances in such techniques as protein purification, affinity chromatography, peptide synthesis, and radioimmunoassay technology permit the translation of recently acquired primary structural data on this important protein into sensitive and specific assays for its circulating derivatives. These assay systems are important tools for probing mechanisms of hemostasis and thrombosis.

Ancrod↗
PubMed1977

Guide wire thrombogenicity measured by fibrinopeptide A radioimmunoassay.

A radioimmunoassay for measurement of canine fibrinopeptide A, which provides a quantitative index of thrombin action on canine fibrinogen, was applied to measurements of the thrombogenicity of angiographic guide wires. Benzalkonium-heparin-treated Teflon-coated, untreated Teflon-coated, and uncoated stainless steel wires were compared in an experiment in dogs which closely simulated the use of these wires in humans. During the first 4 min after insertion, the benzalkonium-heparin-treated Teflon-coated wire was associated with significantly greater systemic levels of fibrinopeptide A than were either Teflon-coated or stainless steel wires. Beyond 10 min, markedly increased levels of fibrinopeptide A were measured in association with these latter two wires compared to the benzalkonium-heparin-treated Teflon-coated wire. Both the early rises in fibrinopeptide A associated with the benzalkonium-heparin-treated Teflon-coated wire and the late increases in fibrinopeptide A associated with the Teflon-coated and uncoated stainless steel wires could be eliminated by prior systemic administration of low dose heparin (40U/kg). These studies suggest that, at least in regard to activation of the plasma clotting system, the benzalkonium-heparin treatment offered no advantages over the other wires tested in terms of reduced thrombogenicity within the critical 10 min following insertion. No difference could be discerned between uncoated stainless steel wires and Teflon-coated stainless steel guide wires in this test.

Angiography↗
PubMed1976

Reactivity of fibrinogen and fibrinopeptide A containing fibrinogen fragments with antisera to fibrinopeptide A.

Two antisera used in the radioimmunoassay for human fibrinopeptide A (FPA) which appear to have different immunochemical specificities have been tested for cross-reactivity with fibrinogen and with three fragments of fibrinogen which contain the FPA sequence. These fragments were the three-chain, NH2-terminal disulfide knot (N-DSK) produced by CNBr cleavage of fibrinogen, the reduced, carboxymethyl Aalpha chain portion of the N-DSK, and fragment E produced by plasmin digestion of fibrinogen. One antiserum (R-2) showed high specificity for free FPA and less than 2% cross-reactivity with fibrinogen or the FPA-containing fragments. The other antiserum (R-33) possessed a much higher degree of cross-reactivity with the FPA-containing fragments. Synthetic and native fibrinopeptides were found to be indistinguishable in the assay system with either antiserum. As a result of these studies, an hypothesis has been developed concerning the nature of the antigenic determinants on FPA which favor measurement of free FPA and limit cross-reactivity with larger, FPA-containing peptides.

Amino Acid Sequence↗
PubMed1976

Immunochemical studies of human fibrinopeptide A using synthetic peptide homologues.

Previous studies have indicated that rabbit antisera R2 and R33 to human fibrinopeptide A differ markedly in terms of cross-reactivity with fibrinogen and fibrinopeptide A-containing fragments of the fibrinogen molecule. Antiserum specificity was characterized by comparison of inhibition of binding to radiolabeled tyrosyl fibrinopeptide A produced by synthetic fragments and enzymatic digests of the fibrinopeptide A molecule vs. the complete fibrinopeptide sequence (Aalpha 1-16). Synthetic COOH-terminal homologues through the dodecapeptide (Aalpha 5-16) exhibited less than 16% immunoreactivity with R33 antiserum, which cross-reacts extensively with fibrinogen and fibrinopeptide A-containing fibrinogen fragments. In contrast, the synthetic COOH-terminal decapeptide (Aalpha 7-16) gave 100% immunoreactivity with R2 antiserum, which cross-reacts minimally with fibrinogen and fibrinopeptide A-containing fibrinogen fragments. Synthetic homologues smaller than Aalpha 7-16, such as Aalpha9-16 and Aalpha 7-11, reacted only minimally with R2 antiserum. Carboxypeptidase B digests of fibrinopeptide A retained less than 25% of their initial immunoreactivity with R2 antiserum. It is concluded that the antigenic determinants of R2 immunoreactivity reside entirely within the COOH-terminal ten-residue sequence of fibrinopeptide A, and that Phe-8, Asp-7, and Arg-16 contribute significantly to R2 immunoreactivity. The R2 antigenic determinants appear to be significantly less accessible to reaction with antibody than the R33 determinants when the fibrinopeptide is attached to its parent alpha chain (Canfield et al., 1976). A possible mechanism for the sequestration is discussed.

Amino Acid Sequence↗
PubMed1976

Specificity of antisera to human fibrinopeptide A used in clinical fibrinopeptide A assays.

Distinction between fibrinopeptide A (FPA) and larger polypeptides containing the FPA sequence is critical for the interpretation of clinical results with FPA immunoassay methods. Therefore, the immunochemical reactivity of 14 rabbit anti-FPA sera with six different FPA containing antigens was studied in detail. Antigens tested included: fibrinogen; fragment E of fibrinogen; the amino-terminal disulfide knot of fibrinogen; Aalpha 1(Ala)-51(Met); Aalpha 1(Ala)-23(Arg); and, FPA. Synthetic partial sequences of FPA were also tested. The 14 FPA-specific antisera were divided into 3 distinct categories with: I, FPA immunoreactivity of larger polypeptides containing FPA approximately 1/100 of FPA on a molar basis, II, FPA immunoreactivity of the larger polypeptides intermediate between I and III; and III, FPA immunoreactivity of the larger polypeptides approximately equal to that of FPA on a molar basis. The antigenic determinants of a category I antiserum (R 2) are included in Aalpha 7(Asp)-16(Arg) with Asp(7), Phe(8) and Arg(16) being essential. When attached to FPA, the sequence Gly(17)-Arg(23) decreases the immunoreactivity of FPA with category I antisera 100-fold. The practical consequence of these findings is that, when category III antisera are employed, both FPA and larger FPA-containing polypeptides are equally immunoreactive. Since thrombin treatment of the larger polypeptides does not alter their immunoreactivity, category III antisera cannot discriminate between FPA and the larger polypeptides. On the other hand, with category I antisera, although the immunoreactivity of FPA itself is unaltered by thrombin treatment, larger polypeptides [e.g., Aalpha 1(Ala)-23tArg)] show a 100-fold increase in immunoreactivity following thrombin treatment and thus can readily be identified and separately quantitated. It is concluded that antisera with the specificity of category I are essential for the specific and accurate measurement of FPA, and for its distinction from larger FPA-containing polypeptides, in clinical plasma samples.

Animals↗
PubMed1975

Natural history of pulmonary thromboemboli in dogs. Serial radiographic observation of clots labeled with powered tantalum.

Powdered tantalum was blown onto the surface of blood clots from 10 dogs. After autologous, tantalum-labeled clots were injected into a systemic vein in each dog, the dogs were sacrificed at varying times over a 5-week period. Microscopic sections showed the tantalum remained attached to the intraluminal clots throughout this period. No appreciable dispersion of label into extravascular parenchyma was observed. Serial roentgenograms demonstrated (a) initially, the labeled clots in the pulmonary arterial tree, (b) lysis of the clots, as indicated by progressive decrease in the breadth of the tantalum labels, (c) peripheral movement of the labeled clots, and (d) eventual fragmentation of the labels.

Animals↗
PubMed1974

Measurement of fibrinopeptide A in human blood.

Since thrombin cleaves fibrinopeptides A (FPA) and B from the NH(2)-terminal end of the fibrinogen molecule, measurement of fibrinopeptide levels in plasma may provide a direct index of thrombin action. Recently a radioimmunoassay for FPA has been developed, and in the present paper, we describe the application of this assay to the measurement of FPA levels in clinical blood samples. Since fibrinogen cross-reacts with antibodies to FPA, dialysis was used to extract the peptide from plasma. In vitro generation of FPA was prevented by removing the fibrinogen from the plasma by precipitation with ethanol before dialysis. The processing technique permitted recovery of 75% of FPA added to blood in vitro. Evidence that the immunoreactivity measured in plasma is due to FPA was provided by the results of experiments in which two antisera to FPA with different specificities showed comparable results and addition of thrombin caused no change in immunoreactivity. In contrast, extracts of streptokinasetreated plasma showed a five-fold increase in activity when treated with thrombin and markedly different immunoreactivity with the two antisera. Plasma FPA levels in 30 normal men were below 2 ng/ml, with a mean of 0.5 ng/ml. FPA levels in 12 patients with reduced fibrinogen levels or reduced platelet counts or both ranged between 4 and 289 ng/ml. FPA levels in 13 patients with normal or elevated fibrinogen levels, including 6 patients with clinical evidence of venous thrombosis or pulmonary embolism or both, ranged between 5 and 23 ng/ml. FPA and fibrinogen degradation product levels did not correlate, and in several patients, elevated FPA levels were found in the presence of normal fibrinogen degradation product levels. After infusion of FPA-containing solutions in four normal individuals, FPA showed a disappearance rate from the plasma consistent with a t((1/2)) of 3-5 min. Heparin infusions in six patients with venous thrombosis or pulmonary embolism or both and elevated FPA levels were followed by a prompt decline in FPA level at a mean rate equivalent to a 3-5 min t((1/2)).

Anticoagulants↗
PubMed1971

Radioimmunoassay of human fibrinopeptide A.

A radioimmunoassay capable of measuring 1 pmole of human fibrinopeptide A has been developed, and should prove useful to detect the release of this peptide from fibrinogen during the coagulation process. Antibodies to fibrinopeptide A were produced by injecting New Zealand white rabbits with a mixture of Freund's adjuvant and native fibrinopeptide coupled to human albumin. N-Tyrosyl fibrinopeptide A was synthesized by the solid-phase method, and was iodinated with (125)I by the Chloramine-T method. 48-73% of the radiolabeled peptide could be bound by the serum of a rabbit immunized with the fibrinopeptide-albumin preparation. Antibody-bound peptide was precipitated by dioxane and was thus separated from unbound peptide. The addition of excess native fibrinopeptide to the radiolabeled material prevented its binding to serum. Native fibrinopeptide A and synthetic fibrinopeptide A were identical in their ability to prevent binding, whereas fibrinogen was from 1/25,000 to 1/50,000 as effective on a weight basis. Plasma filtered through a membrane relatively impermeable to molecules larger than a molecular weight of 34,000 showed no fibrinopeptide reactivity, whereas a similar filtrate of serum gave quantitative recovery of fibrinopeptide reactivity.

Albumins↗