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The American Journal of Pathology Dec 1990Recently evidence was provided for a pathway whereby circulating fibrinogen enters megakaryocyte granules by an endocytic mechanism. Synthesis of fibrinogen by...
Recently evidence was provided for a pathway whereby circulating fibrinogen enters megakaryocyte granules by an endocytic mechanism. Synthesis of fibrinogen by megakaryocytes has been reported. To determine the relationship between plasma fibrinogen and alpha-granule fibrinogen in megakaryocytes and platelets, the fibrinogen content of these cells was studied in rats defibrinated by use of Ancrod, a thrombinlike enzyme purified from the venom of Agkistrodon rhodostoma. Unlike thrombin, Ancrod does not induce platelet secretion. Rats were injected with Ancrod (50 units/kilogram body weight) at 8-hour intervals for 5 days. There were no significant changes in platelet counts. Blood from the treated rats failed to clot, and plasma fibrinogen levels were less than 15 mg/dl. Bone marrow from defibrinated rats and untreated control rats was stained immunohistochemically for fibrinogen and two other alpha-granule proteins, albumin and platelet factor 4 (PF4), in plastic-embedded sections. The presence of these three proteins in platelets was detected by Western blots. Only trace amounts of fibrinogen were detected in megakaryocytes and platelets from defibrinated rats, but fibrinogen in control megakaryocytes and platelets was readily demonstrated. However defibrinated and control rats did not differ in albumin and PF4 content in megakaryocytes and platelets. It is concluded that a major portion of rat platelet fibrinogen is derived from plasma by endocytosis by megakaryocytes.
Topics: Ancrod; Animals; Blood Platelets; Blotting, Western; Fibrin; Fibrinogen; Megakaryocytes; Platelet Count; Platelet Factor 4; Rats; Rats, Inbred Strains; Serum Albumin
PubMed: 2260627
DOI: No ID Found -
Journal of Vascular Surgery Dec 1997Digital gangrene was observed in a patient who had angiographic findings of digital arterial occlusion. The patient's blood showed a marked red blood cell aggregation... (Review)
Review
Digital gangrene was observed in a patient who had angiographic findings of digital arterial occlusion. The patient's blood showed a marked red blood cell aggregation with rouleaux formation in long chains, which could not be dispersed at shear rates up to 200 sec-1. Studies of the patient's blood revealed the presence of an abnormal fibrinogen capable of aggregating normal red blood cells. This fibrinogen was found by Raman spectroscopy to have an increased alpha-helical content, whereas the beta-sheet content was decreased. Defibrinogenation therapy with ancrod resulted in a dramatic symptomatic relief. The disappearance of the abnormal fibrinogen 6 months later and an absence of a family history indicate that this dysfibrinogenemia was acquired.
Topics: Arterial Occlusive Diseases; Erythrocyte Aggregation; Fibrinogen; Fingers; Gangrene; Humans; Male; Middle Aged
PubMed: 9423724
DOI: 10.1016/s0741-5214(97)70021-1 -
The Journal of Clinical Investigation Jul 1998In rheumatoid arthritis, synovial expression of urokinase (uPA) activity is greatly increased (Busso, N., V. Péclat, A. So, and A. -P. Sappino. 1997. Ann. Rheum. Dis....
In rheumatoid arthritis, synovial expression of urokinase (uPA) activity is greatly increased (Busso, N., V. Péclat, A. So, and A. -P. Sappino. 1997. Ann. Rheum. Dis. 56:550- 557). We report the same effect in murine antigen-induced arthritis. uPA-mediated plasminogen activation in arthritic joints may have deleterious effects via degradation of cartilage and bone matrix proteins as well as beneficial effects via fibrin degradation. We evaluated these contrasting effects in vivo by analyzing the phenotype of uPA-deficient (uPA-/-) and control mice during antigen-induced arthritis. Joint inflammation was comparable in both groups up to day 3 and subsequently declined in control mice, remaining significantly elevated in uPA-/- mice on days 10 and 30 after arthritis onset. Likewise, synovial thickness was markedly increased in uPA-deficient mice persisting for up to 2 mo, whereas it subsided in control animals. Bone erosion was exacerbated in uPA-/- mice on day 30. By contrast, no difference in articular cartilage proteoglycan content was found between both groups. Significantly increased accumulation of fibrin was observed by day 30 in arthritic joints of uPA-/- mice. We hypothesized that synovial fibrin deposition plays a role in joint inflammation. Accordingly, defibrinogenation of uPA-/- mice by ancrod significantly decreased the sustained joint inflammation. All the above observations were reproducible in plasminogen-deficient (Pln-/-) mice. In conclusion, synovial fibrin deposition plays a role as a nonimmunological mechanism which sustains chronic arthritis.
Topics: Animals; Antigens; Arthritis; Fibrin; Fibrinogen; Interleukin-1; Mice; Mice, Inbred C57BL; Synovial Membrane; Urokinase-Type Plasminogen Activator
PubMed: 9649555
DOI: 10.1172/JCI2312 -
Microbes and Infection Feb 2004Clumping factor A (ClfA), a fibrinogen-binding protein expressed on the Staphylococcus aureus cell surface, has previously been shown to act as a virulence factor in...
Clumping factor A (ClfA), a fibrinogen-binding protein expressed on the Staphylococcus aureus cell surface, has previously been shown to act as a virulence factor in experimental septic arthritis. Although the interaction between ClfA and fibrinogen is assumed to be of importance for the virulence of S. aureus, this has not been demonstrated in any in vivo model of infection. Therefore, the objective of this study was to investigate the contribution of this interaction to ClfA-mediated virulence in murine S. aureus-induced arthritis. Ancrod, a serine protease with thrombin-like activity, was used to induce in vivo depletion of fibrinogen in mice. Ancrod treatment significantly aggravated septic arthritis following inoculation with a ClfA-expressing strain (Newman) compared to control treatment. Also, ancrod treatment tended to enhance the arthritis induced by a clfA mutant strain (DU5876), indicating that fibrinogen depletion exacerbates septic arthritis in a ClfA-independent manner. Most importantly, the ClfA-expressing strain was much more arthritogenic than the isogenic clfA mutant, following inoculation of fibrinogen-depleted mice. This finding indicates that the interaction between ClfA and free fibrinogen is not required for ClfA-mediated functions contributing to S. aureus virulence. It is conceivable that ClfA contributes to the virulence of S. aureus through interactions with other host ligands than fibrinogen.
Topics: Animals; Coagulase; Fibrinogen; Mice; Mice, Inbred Strains; Staphylococcal Infections; Staphylococcus aureus; Virulence
PubMed: 14998518
DOI: 10.1016/j.micinf.2003.10.014 -
The Journal of Biological Chemistry Nov 2005Protein C activation initiated by the thrombin-thrombomodulin complex forms the major physiological anticoagulant pathway. Agkistrodon contortrix contortrix protein C...
Thrombomodulin-independent activation of protein C and specificity of hemostatically active snake venom serine proteinases: crystal structures of native and inhibited Agkistrodon contortrix contortrix protein C activator.
Protein C activation initiated by the thrombin-thrombomodulin complex forms the major physiological anticoagulant pathway. Agkistrodon contortrix contortrix protein C activator, a glycosylated single-chain serine proteinase, activates protein C without relying on thrombomodulin. The crystal structures of native and inhibited Agkistrodon contortrix contortrix protein C activator determined at 1.65 and 1.54 A resolutions, respectively, indicate the pivotal roles played by the positively charged belt and the strategic positioning of the three carbohydrate moieties surrounding the catalytic site in protein C recognition, binding, and activation. Structural changes in the benzamidine-inhibited enzyme suggest a probable function in allosteric regulation for the anion-binding site located in the C-terminal extension, which is fully conserved in snake venom serine proteinases, that preferentially binds Cl(1-) instead of SO(4)(2-).
Topics: Agkistrodon; Allosteric Regulation; Amino Acid Sequence; Ancrod; Animals; Benzamidines; Catalytic Domain; Crotalid Venoms; Crystallography, X-Ray; Hemostasis; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Models, Molecular; Molecular Sequence Data; Peptides; Protein C; Protein Conformation; Sequence Homology, Amino Acid; Serine Proteinase Inhibitors; Static Electricity; Thrombomodulin
PubMed: 16162508
DOI: 10.1074/jbc.M508502200 -
The American Journal of Pathology Dec 2000Functional inhibition of tissue factor (TF) has been shown to improve coronary blood flow after myocardial ischemia/reperfusion (I/R) injury. TF initiates the...
Functional inhibition of tissue factor (TF) has been shown to improve coronary blood flow after myocardial ischemia/reperfusion (I/R) injury. TF initiates the coagulation protease cascade, resulting in the generation of the serine protease thrombin and fibrin deposition. Thrombin can also contribute to an inflammatory response by activating various cell types, including vascular endothelial cells. We used a rabbit coronary ligation model to investigate the role of TF in acute myocardial I/R injury. At-risk areas of myocardium showed increased TF expression in the sarcolemma of cardiomyocytes, which was associated with a low level of extravascular fibrin deposition. Functional inhibition of TF activity with an anti-rabbit TF monoclonal antibody administered either 15 minutes before or 30 minutes after coronary ligation reduced infarct size by 61% (P = 0.004) and 44% (P = 0.014), respectively. Similarly, we found that inhibition of thrombin with hirudin reduced infarct size by 59% (P = 0.014). In contrast, defibrinogenating the rabbits with ancrod had no effect on infarct size, suggesting that fibrin deposition does not significantly contribute to infarct size. Functional inhibition of thrombin reduced chemokine expression and inhibition of either TF or thrombin reduced leukocyte infiltration. We propose that cardiomyocyte TF initiates extravascular thrombin generation, which enhances inflammation and injury during myocardial I/R.
Topics: Animals; Antibodies, Monoclonal; Antithrombins; Cell Movement; Chemokines; Fibrin; Fibrinogen; Hirudins; Microscopy, Electron; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocarditis; Myocardium; Neutrophils; Rabbits; Thrombin; Thromboplastin
PubMed: 11106558
DOI: 10.1016/S0002-9440(10)64824-9 -
Journal of Neurology, Neurosurgery, and... Aug 1988Plasma hyperviscosity is a striking abnormality in patients suffering from subcortical arteriosclerotic encephalopathy (SAE) and is thought to perpetuate the chronic... (Clinical Trial)
Clinical Trial
Plasma hyperviscosity is a striking abnormality in patients suffering from subcortical arteriosclerotic encephalopathy (SAE) and is thought to perpetuate the chronic ischaemic demyelinating process of the periventricular white matter. Ancrod, a defibrinating enzyme, was given to 10 patients with SAE in an attempt to reduce plasma fibrinogen, which would thus normalise hyperviscosity. This was paralleled by a significant improvement of the initially abnormal retinal arteriovenous passage time, as well as a significant augmentation of the CO2-induced cerebral vasomotor response. This did not lead, however, to any clinical improvement with respect to performance of neuropsychological tests, recurrences of strokes during a 6 month observation period or improvement of various audiological parameters. The findings indicate that hyperviscosity in patients with SAE is merely an epiphenomenon. A potentially reversible, chronic penumbral state of the brain tissue apparently does not exist in SAE.
Topics: Aged; Ancrod; Blood Viscosity; Brain Ischemia; Clinical Trials as Topic; Dementia, Multi-Infarct; Fibrinogen; Follow-Up Studies; Humans; Hypertension; Intracranial Arteriosclerosis; Prospective Studies; Rheology
PubMed: 3063776
DOI: 10.1136/jnnp.51.8.1051 -
American Journal of Physiology. Heart... Aug 2004The role of active thrombosis in the pathophysiology of pulmonary embolism is unclear. We tested the hypothesis that venous thrombi significantly increase their...
The role of active thrombosis in the pathophysiology of pulmonary embolism is unclear. We tested the hypothesis that venous thrombi significantly increase their thrombotic activity once they embolize into the high-flow circulation of the pulmonary arteries. Thrombotic activity was measured using an immunoassay that measures both fibrinopeptide B (FPB) as well as its most abundant metabolite des-arginine FPB. Thrombi were formed in the femoral veins of adult dogs. In one group, the thrombi were embolized without anticoagulation. In the second group, heparin (300 U/kg bolus, then 90 U x kg(-1) x h(-1) infusion) was administered before embolization to prevent subsequent thrombotic activity. Plasma FPB concentrations were significantly suppressed in the heparinized group relative to the nonheparinized group for 1 h postembolization (P = 0.038). We conclude that pulmonary embolization itself causes preexisting venous thrombi to greatly intensify their thrombotic activity and that embolization-associated thrombus propagation can be prevented by heparin.
Topics: Ancrod; Animals; Anticoagulants; Dogs; Fibrinogen; Fibrinopeptide B; Heparin; Humans; Male; Pulmonary Embolism; Thromboembolism; Thrombosis
PubMed: 15044200
DOI: 10.1152/ajpheart.01197.2003 -
British Medical Journal Oct 1974The effect of a low-dosage regimen of ancrod in the prevention of postoperative deep vein thrombosis was assessed in 24 patients having surgical repair of fractured neck... (Clinical Trial)
Clinical Trial
The effect of a low-dosage regimen of ancrod in the prevention of postoperative deep vein thrombosis was assessed in 24 patients having surgical repair of fractured neck femur and compared with 25 control patients who did not receive therapy. The objective of the therapy was to lower the preoperative fibrinogen level and produce a low concentration of fibrin degradation products yet avoid the haemorrhagic complications of total defibrination. Ancrod therapy proved feasible to carry out, was not associated with haemorrhagic complications, and produced sustained, predictable reductions in fibrinogen concentration. There were seven thromboembolic complications in the control patients compared to one such complication in the ancrod-treated patients. Five deaths occurred in the control group and one in the treated group. Though the incidence of deep vein thrombosis was not apparently affected by ancrod it appeared on venography that the thrombi in the treated patients were less extensive than those in the control patients. Finally, some discrepancies in the diagnosis of deep vein thrombosis by the three techniques of clinical examination, (125)I-fibrinogen scanning, and ascending venography were identified.
Topics: Aged; Anticoagulants; Clinical Trials as Topic; Female; Femoral Neck Fractures; Fibrin; Fibrinogen; Hemagglutination Inhibition Tests; Humans; Injections, Intravenous; Iodine Radioisotopes; Peptide Hydrolases; Phlebography; Postoperative Complications; Radionuclide Imaging; Thromboembolism; Thrombophlebitis; Venoms
PubMed: 4607845
DOI: 10.1136/bmj.4.5937.130 -
British Journal of Experimental... Aug 1976It is shown that after a single i.v. dose of [131I]-polyvinylpyrrolidone ([131I]-PVP) the total body and plasma radioactivities of rabbits decrease at distinctly...
It is shown that after a single i.v. dose of [131I]-polyvinylpyrrolidone ([131I]-PVP) the total body and plasma radioactivities of rabbits decrease at distinctly different rates. The difference between these two rates is utilized to calculate the phagocytic rate of [131I]-PVP by reticuloendothelial cells.A number of experimental conditions are reported in which enhanced reticuloendothelial uptake of [131I]-PVP is readily demonstrable. They include the injection of small quantities of heterologous plasma, certain proteolytic fragments of the fibrinogen molecule, the clearance of antigen-antibody complexes, and the acute phase reaction (inflammatory response) as brought about by serum sickness, sterile abscess and vaccination. Based on these observations it is suggested that [131I]-PVP may provide a convenient technique for the long-term monitoring of the activity of reticuloendothelial cells, presumably mainly that of the histiocytes. The pronounced polydispersity of commercially available [131I]-PVP is a serious problem in this respect which can be largely overcome, but not completely abolished, by the screening techniques described herein. Post-mortem analyses of rabbit tissues showed most of the [131I]-PVP to be present in the skin (20%), followed by the liver (14%), bone marrow (10%), muscle (7%) and kidney (5%). Gel filtration studies with [131]-PVP in the presence and in the absence of plasma proteins failed to demonstrate any association between PVP and the proteins. [131I]-PVP kept at physiological pH and 37 degrees C lost less than 5% of its radioactivity over one month due to spontaneous deiodination.
Topics: Ancrod; Animals; Antigen-Antibody Complex; Chromatography, Gel; Fibrinogen; Iodine Radioisotopes; Mononuclear Phagocyte System; Phagocytosis; Povidone; Rabbits; Rats; Vaccines
PubMed: 971408
DOI: No ID Found