Thromb Haemostasis
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Conventional laboratory methods were used to screen untreated tumor-bearing dogs for hemostatic abnormalities. Excluded from study were dogs with clinical evidence of bleeding. The primary site for neoplastic disease in 100 dogs studied included hemolymphatic system, skin, bone, thyroid gland, oropharynx, mammary gland, and nasal cavity. ⋯ Sixteen dogs had positive protamine sulfate (paracoagulation) reaction, and 8% had increased plasma fibrin degradation products. The euglobulin lysis time was accelerated in 24% of the dogs, and 15% had schistocytes on blood film. These data indicate that the majority of dogs with advanced neoplasms are likely to have abnormal coagulation tests.
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Using the chromogenic substrate, Tos-Gly-Pro-Arg-pNA-HCl (Chromozym TH, Boehringer Mannheim) plasma thrombin was estimated in six cases of envenomation by Australian elapid snakes. All patients manifested findings characteristic of defibrination due to envenomation by these snakes. Fibrin-fibrinogen degradation products were grossly elevated, as was plasma thrombin in all cases. Following treatment with antivenene, all abnormal coagulation parameters returned rapidly towards normal by 24 hours and plasma thrombin disappeared.
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In dilute suspensions of platelet-rich plasma (PRP) or gel-separated platelets (GSP), dibutyryl-cAMP (DBcAMP) and monobutyryl-cAMP inhibited platelet-mediated fibrin clot retraction in concentrations of 2--3 X 10(-6) M, with complete inhibition at 1--3 X 10(-4) M. Prostaglandin E1 (PGE1), which inhibited fibrin clot retraction in concentrations greater than 1.5--3 X 10(-8) M, was a more effective inhibitor than either PGE2 or PGF2 alpha. In the presence of theophylline (10-4 M), concentrations of DBcAMP, PGE1, PGE2 and PGF2 alpha necessary to inhibit fibrin clot retraction were reduced 50-fold for DBcAMP and 2.5 to 20-fold for the prostaglandins. ⋯ Thus, compounds which increase platelet cAMP levels result in the inhibition of platelet-mediated fibrin clot retraction, and this inhibitory effect may be mediated, at least in part, through suppression of platelet contractility. Cyclic GMP, dibutyryl-cGMP and carbamylcholine-Cl (which stimulate guanylate cyclase) did not influence fibrin clot retraction, and did not prevent inhibition of fibrin clot retraction by DBcAMP and PGE1. Colchicine, in concentrations known to disrupt platelet microtubules (2.5 X 10(-6) M to 2.5 X 10(-3) M), had little inhibitory effect on either fibrin clot retraction or platelet (3H)-serotonin release.
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Human fibrinogen was treated at pH 6.0, 7.3 and 9.0 with thrombin, batroxobin (thrombin-like fraction of Bothrops atrox venom) or an extract of the venom from Ancistrodon contortrix contortrix. These three enzymes released the NH2-terminal fibrinopeptides A and B at different rates. Thrombin-free, preactivated factor XIII (factor XIIIa) was added to incubation mixtures to stabilize resulting fibrin(ogen) aggregates. ⋯ However, when fibrinopeptide B was removed with the contortrix enzyme, soluble cross-linked oligomers appeared initially. The opaque fibrin clots, produced by thrombin (pH 6.0) or contortrix procoagulant fraction (pH 7.3), were found to be devoid of alpha-polymers even after prolonged incubation with factor XIIIa. Our data suggest that the solubility and opacity of fibrin networks are not primarily related to the type of the cross-link (gamma-gamma versus alpha-alpha interactions).
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The authors compared the oxygen consumption in platelets from the umbilical cord blood of 36 healthy newborn infants with that of 27 adult subjects, before and after thrombin addition (1.67 U/ml). Oxygen consumption at rest was 6 mumol/10(9)/min in adult control platelets and 5.26 in newborn infants. The burst in oxygen consumption after thrombin addition was 26.30 mumol/10(9)/min in adults and 24.90 in infants. ⋯ Deoxyglucose inhibited the burst in O2 consumption in newborn infant and adult platelets by about 50%. KCN at the concentration of 10(-4) M completely inhibited basal oxygen consumption but did not completely inhibit the burst after thrombin. At the concentration of 10(-3) M, it inhibited both basal O2 consumption and the burst in infants and adult subjects.