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PubMed1981

Essential athrombia. A report on 4 cases from South India.

Four cases of essential athrombia have been diagnosed in the 14 year period from June, 1966 to June, 1980 at the Coagulation Laboratory of the Christian Medical College Hospital, Vellore. All cases fit Inceman's description of the original case and fulfill the diagnostic criteria of prolonged bleeding time, decreased platelet aggregation, normal platelet count, normal morphology and normal clot retraction. No cases have been reported from India in the past 15 years.

Adolescent↗
PubMed2001

Platelet activation by sustained exposure to low-dose plasmin.

Plasmin has been reported to activate and inhibit platelet function depending on dose and exposure temperature. The present study examines the induction of fibrinogen-dependent platelet aggregation following prolonged (60 min) platelet exposure to very low doses of plasmin (0.05 CU/ml) at either 22 or 37 degrees C. Maximum aggregation [mean +/- SD, 60 +/- 19 light transmission units (LTU); n = 43] occurred following platelet exposure to plasmin at 22 degrees C, but significant platelet aggregation (28 +/- 4 LTU, n = 3) also occurred following plasmin treatment at 37 degrees C. Plasmin-induced platelet aggregates appeared microscopically larger than aggregates of adenosine diphosphate (ADP)-activated platelets, and were less reversible. Aggregated plasmin-treated platelets also expressed more procoagulant activity than platelets aggregated with ADP, as reflected by shortening of the plasma kaolin recalcification time. Aggregation of platelets exposed to very low doses of plasmin was not accompanied by dense or alpha-granule secretion, and was unaffected by ADP antagonists or aspirin. Partial inhibition of platelet aggregation, however, was achieved with metabolic inhibitors, PGE1, and inhibitors of phosphoinositide 3-kinase or protein kinase C. Although fibrinogen was required for plasmin-treated platelet aggregation, [125I]-fibrinogen binding comprised only 58 +/- 3% (n = 3) of fibrinogen binding associated with ADP aggregated platelets. This was consistent with observed decreases in reptilase-induced fibrin clot retraction. Taken together, these data suggest that sustained exposure of platelets to very low plasmin doses leads to platelet activation and thus may contribute to thrombotic complications in vivo.

Adenosine Diphosphate↗
PubMed2005

Integrin-dependent interaction of lipid rafts with the actin cytoskeleton in activated human platelets.

Dynamic connections between actin filaments and the plasma membrane are crucial for the regulation of blood platelet functions. Protein complexes associated with alphaIIbbeta3 integrin-based cytoskeleton structures are known to play a role in these processes. However, mechanisms involving lateral organizations of the plasma membrane remain to be investigated. Here, we demonstrate that a large fraction of platelet lipid rafts specifically associates with the actin cytoskeleton upon activation. This association was inhibited by antagonists of fibrinogen-alphaIIbbeta3 binding and did not occur in type I Glanzman's thrombasthenic platelets. The raft-cytoskeleton interaction is a reversible process correlating with the intensity and stability of platelet aggregation. Although only a minor fraction of alphaIIbbeta3 was recovered in rafts upon activation, this integrin specifically upregulated the level of PtdIns(4,5)P2 in membrane microdomains and induced the recruitment of several actin-modulating proteins known to directly or indirectly interact with this lipid. Controlled disruption of rafts did not affect alphaIIbbeta3-mediated platelet aggregation in response to high concentrations of thrombin but significantly inhibited fibrin clot retraction. We propose that rafts participate in the organization of membrane-cytoskeleton interactions where alphaIIbbeta3-mediated tension forces apply during the late phase of platelet activation.

Actin Cytoskeleton↗
PubMed1990

[Multivariate analysis for the understanding of typical diabetic hemostasis criteria. 2. Prevalent thrombocytic markers].

Various thrombocyte functions and metabolic criteria were investigated in 309 test persons, among them 198 Patients affected with diabetes mellitus, 67 of type I and 131 of type II as well as 111 healthy control persons. From the variety of these factors an optimal amount was determined by means of the statistical method of multivariance analysis separating both types of diabetes and healthy control persons. In addition to haemoglobin A1 concentration, thrombocyte parameters have been found together with the degree of capillary fragility, adrenalin-induced aggregation, platelet aggregation test and clot retraction, which allow individuals to be assigned diagnostically to various groups of test persons. Thus, thrombocyte functions found in both types of diabetes and normal persons exhibit differences which may contribute to a diagnostic classification.

Adult↗
PubMed1995

Influence of teniposide on platelet functions in vitro.

Teniposide added to citrated platelet-rich plasma reduced platelet aggregation induced by collagen, but did not interfere with ADP-induced aggregation. The availability of platelet factor 3 was decreased irrespective of inducer. Reptilase clot retraction induced by ADP or collagen was reduced. Teniposide did not interfere with platelet adhesion to glass. It did not release lactic dehydrogenase from the cytoplasm of platelets. Coagulation factors were not affected.

Adenosine Diphosphate↗
PubMed2003

Görög Thrombosis Test: a global in-vitro test of platelet function and thrombolysis.

This is the first laboratory evaluation of a new instrument, designed to test both platelet function and thrombolytic activity from a native blood sample, in vitro. The inventor assumed that the reduction and arrest of blood flow was due to activation, aggregation and stabilized thrombus formation by shear-activated platelets, and that re-establishment of flow was due to thrombolysis. Morphologic and functional studies presented here confirm these mechanisms. In vitro tests provided incontestable evidence for the principal role of platelets in the obstruction of flow (occlusion time) and for thrombolysis as the principal mechanism underlying the restoration of blood flow (lysis time). In addition to aggregation, it is the explosive generation of thrombin by shear-activated platelets that results in the formation of an occlusive haemostatic thrombus. Anticoagulation of blood completely prevented occlusion. Platelet-rich thrombus formation (occlusion time) was dose-dependently inhibited by monoclonal antibody against platelet glycoprotein (GP) Ib (6B4 and 12E4), aurin tricarboxylic acid, monoclonal antibody against platelet GPIIb/IIIa (MA-16N7C2 and abciximab), a synthetic GPIIb/IIIa antagonist (TAK-029), thrombin inhibitor (argatroban), and anti-von Willebrand factor, but not by anti-fibrinogen. Plasminogen activator streptokinase (Varidase) and tissue-type plasminogen activator (Monteplase) dose-dependently enhanced thrombolysis (lysis time) without affecting platelet function (occlusion time). The test is specific for thrombolysis. The plasmin inhibitor tranexamic acid prevented plasminogen activator-induced thrombolysis, while inhibition of clot retraction by cytochalasin B did not affect the lysis time. This rapid and sensitive global test of platelet function and thrombolytic activity could be of great value both in research and in clinical practice.

Adult↗
PubMed1982

Protein and glycoprotein abnormalities in an unusual subtype of Glanzmann's thrombasthenia.

A patient with Glanzmann's thrombasthenia has been analysed by high resolution two-dimensional polyacrylamide gel electrophoresis and crossed immunoelectrophoresis. Although clot retraction is subnormal, glycoproteins IIb and IIIa are completely absent and platelet fibrinogen is strongly reduced indicating an unusual subtype of type II thrombasthenia. No changes in the pI of glycoproteins have been observed. Heterogeneity in Glanzmann's thrombasthenia is discussed.

Blood Platelets↗
PubMed1993

Immunoglobulins from normal sera bind platelet vinculin and talin and their proteolytic fragments.

Our previous finding that normal serum immunoglobulins bind to internal platelet proteins on Western blots led us to further identify these proteins and determine the possible significance of autoantibodies against them. A 95-Kd protein reactive with immunoglobulins in most normal sera and easily confused with gpIIIa was shown to be a fragment of vinculin generated by calpain proteolysis. Identity was established by peptide sequencing of the protein purified from platelets stored without specific protease inhibitors. Normal immunoglobulins bound intact vinculin (117 Kd) and metavinculin (152 Kd), and their 105-, 95-, and 80- to 85-Kd proteolytic fragments. IgG in 89%, and IgA and IgM in 100% of normal sera reacted in titers of 10 to 1,000 with purified vinculin. In addition, IgG in 79%, and IgA and IgM in 93% of normal sera reacted in titers of 10 to 5,000 with talin (235 Kd), another cytoskeletal protein, and its 200-Kd proteolytic fragment. IgGs in sera from animals of several different phylogenetic classes also reacted with human vinculin and talin on Western blots. Frequency of occurrence, titers, and classes of antivinculin and antitalin autoantibodies in patients with thrombocytopenia did not differ discernibly from those of normal individuals. These antibodies had no effect on platelet aggregation or clot retraction, and no apparent pathogenic significance, but their widespread presence and the variability in extent of proteolysis of platelet preparations used for Western blots can complicate interpretation of patterns obtained with sera from patients with presumed immune-mediated thrombocytopenias.

Antibodies, Monoclonal↗
PubMed1989

Vena caval filter splaying: potential complication of use of the titanium Greenfield filter.

Significant structural and mechanical differences exist between the titanium and stainless steel versions of the Greenfield filter (GF). The titanium GF has a longer leg length (49 mm vs 43 mm), a greater span (38.5 mm vs 28.0 mm), and a larger hook angle (41 degrees vs 23.5 degrees). In vitro tests demonstrated approximately sevenfold greater filter length shortening (a measure of filter splaying) for the titanium GF in response to a given applied load. These differences resulted in marked filter splaying and inferior vena cava (IVC) perforation in three patients in whom a titanium GF had been inserted. The aorta was penetrated by a filter leg in one patient, and abdominal or back pain was present in all three patients. In vitro tests involving thrombosis within a latex balloon revealed that the titanium GF, but not the stainless steel GF, remained splayed even in the face of clot retraction. Design modifications, possibly using shorter, thicker filter legs and using reduced hook angles, should be made in the titanium GF to decrease the risk of filter splaying and IVC perforation before widespread use of this device.

Adult↗
PubMed1971

Effect of a new antiaggregating chemical on the structure and function of the human platelet.

A new antiaggregating chemical, alpha-(p-(fluoren-9-ylidenemethyl)phenyl)-2-piperidineethanol (RMI 10,393), designated FYPE, was found to be an effective inhibitor of platelet aggregation induced by adenosine diphosphate (ADP), thrombin, collagen, or epinephrine. Effects of the antiaggregant on platelets were concentration dependent. Aggregation was prevented by low concentrations of FYPE that produced in the platelet only minor ultrastructural changes consisting of loss of microtubules and of discoid shape. Low levels of FYPE that prevented platelet aggregation had no effect on platelet ATPase activities but did alter clot retraction, the thrombin-induced shift in electrophoretic mobility and platelet cholinesterase activity. Market decrease in ADP release and increase in adenyl cyclase activity were produced by low levels of FYPE. This study provides a model for evaluation of platelet antiaggregating compounds in vitro.

Adenosine Diphosphate↗
PubMed1978

Platelet hyperaggregability and thrombosis in patients with thrombocythemia.

The relation between platelet hyperaggregability and thrombosis was assessed in 28 patients with thrombocythemia due to myeloproliferative diseases and 11 with reactive thrombocytosis. None of the patients with reactive thrombocytosis had thrombotic or hemorrhagic complications, but thrombosis was noted in seven patients and bleeding in two patients with thrombocythemia. Nineteen were asymptomatic. In patients with thrombosis, bleeding time, platelet glass retention, and clot retraction were normal, but evidence of platelet hyperaggregability was present in all but one. Serial studies on six patients revealed a close association between platelet hyperaggregability and ischemic attacks. Neither patient with bleeding complications had evidence of platelet hyperaggregability, although poor platelet function was found in one. Platelet function in asymptomatic patients can be classified as hyperactive, hypoactive, or normal.

Adult↗
PubMed2001

Effects of alpha-tocopherol on platelets and the coagulation system.

Vitamin E is one of the most widely used antioxidants in cryopreservation and preservation technology. The objective of this study is to examine the effect of vitamin E on platelets and the coagulation system. Vitamin E was added at different concentrations in the range between 0.25 and 5 mM to donor plasma. Using a STA/STA Compact coagulation analyzer the following clotting tests were performed: prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT). The control clotting times PT (13.80 +/- 0.4 s), APTT (27.4 +/- 2.4 s) and TT (17.6 +/- 0.4 s) remained unchanged in the presence of vitamin E. The effect of vitamin E on platelets was assessed by platelet-induced clot retraction (PICR) and aggregation by thrombin. PICR was unaffected by vitamin E. Platelet aggregation, however, was profoundly inhibited by vitamin E. We found that inhibition of platelet aggregation by vitamin E was concentration dependent: increasing with increasing vitamin E concentration. This inhibitory effect, however, was widely reversible upon dilution of vitamin E with autologous platelet-poor plasma.

Blood Coagulation↗
PubMed1984

[Pharmacological studies of FUT-175, nafamstat mesilate. IV. Effects on coagulation, platelets and fibrinolysis].

Inhibitory effects of FUT-175 (nafamstat mesilate) on coagulation, platelets and fibrinolysis were examined. FUT-175 prolonged activated partial thromboplastin time, thrombin time and prothrombin time in rabbit plasma. FUT-175 prolonged these coagulation times in human plasma at lower concentration than in rabbit plasma. FUT-175 inhibited platelet aggregation induced by a variety of aggregation agents in rabbit platelet-rich plasma (PRP). In human PRP, FUT-175 inhibited platelet aggregation induced by a variety of aggregation agents at lower concentration than in rabbit PRP. Lipopolysaccharide induced a dose-dependent platelet aggregation in dog PRP. FUT-175 showed an inhibitory effect on this aggregation. FUT-175 inhibited clot retraction in rabbit plasma. The fibrinolysis activity was measured on fibrinolysis of rabbit plasma activated by urokinase. FUT-175 prolonged this fibrinolysis time. Inhibitory effects on coagulation and fibrinolysis were also found ex vivo. FUT-175 prolonged bleeding time in mice. These results indicate that FUT-175 has potent inhibitory effects on coagulation, platelets and fibrinolysis.

Animals↗
PubMedDate not supplied

[Effect of phosphatidylserine on formation and lysis of fibrin].

Phosphatidyl serine inhibited non-enzymatic step of fibrin formation (selfassociation of monomeric fibrin). But phosphatidyl serine did not affect the factor XIII activity, the rate of fibrin clot retraction and its tolerance to plasmin. Activity of plasmin was not altered in presence of phosphatidyl serine but influence of slowly acting antiplasmin on plasmin was slightly limited by the lipoid. Due to this phenomenon phosphatidyl serine caused the activation of fibrinolysis in native system (blood plasma). The data obtained support the earlier advanced assumptions on inhibition of thrombin-fibrinogene reaction by phosphatidyl serine.

Antifibrinolytic Agents↗
PubMed1983

Influence of a microtubule stabilizing agent on platelet structural physiology.

Unstimulated blood platelets have a characteristic discoid form supported by a circumferential band of microtubules. After exposure to aggregating agents, platelets lose their lentiform shape and become irregularly convoluted, with many pseudopods. The changes in surface contour are associated with a process of internal transformation. Randomly dispersed granules are concentrated in cell centers and enclosed within tight-fitting rings of microtubules and microfilaments. The mechanism involved in the shift of circumferential microtubules into rings encircling clumped granules is uncertain. Recent studies have suggested that microtubules are disassembled shortly after stimulation and reassemble in new locations a few minutes later. Taxol, a microtubule stabilizing agent, has been used in the present study to evaluate the disassembly-reassembly hypothesis of internal transformation in activated platelets. Stabilization of microtubules by taxol did not injure platelet biochemistry or structure. Concentrations of taxol that protected platelet microtubules from dissociation by cold or vincristine did not inhibit platelet shape change, pseudopod formation, internal transformation, secretion, aggregation, or clot retraction. The number of microtubules wrapped around centrally clumped granules, present in pseudopods or spread through the cytoplasm, was equal to or greater than that found in untreated platelets following activation and aggregation. Though it is possible that microtubules dissolve in platelets following activation, the results of this study demonstrate that such an event is not essential for any aspect of the physiologic response of platelets in hemostasis.

Alkaloids↗
PubMed1984

Mechanism of action of the platelet aggregation inhibitor purified from Agkistrodon halys (mamushi) snake venom.

The platelet aggregation inhibitor purified from Agkistrodon halys snake venom inhibited rabbit platelet aggregations induced by thrombin, sodium arachidonate, collagen or ionophore A-23187. The IC50 was about 11 micrograms/ml in platelet aggregation regardless of which aggregation inducer was used. beta-Mercaptoethanol abolished both the phospholipase A enzymatic and platelet aggregation inhibitory activities of this venom inhibitor. p-Bromophenacyl bromide-treated venom inhibitor lost almost completely its phosphilipase A enzymatic activity, but retained its platelet aggregation inhibitory effect. In the presence of EGTA, the venom inhibitor still showed the same inhibitory activity on thrombin-, sodium arachidonate-, collagen- or ionophore A23187-induced platelet aggregations triggered by successive addition of Ca2+. The activation of platelet phospholipase A and the serotonin release reaction triggered by Ca2+ influx were unaffected by this venom inhibitor. It also inhibited the clot retraction of platelet-rich plasma. It is concluded that the inhibitory effect of the venom inhibitor on platelet aggregation is independent of its phospholipase A enzymatic activity. Its mode of action is different from those of other known platelet inhibitory drugs. This venom inhibitor possibly acts on a common step subsequent to platelet shape change, leading to inhibition of platelet aggregation.

Animals↗
PubMed1993

Effects of Poloxamer 188 on fibrin network structure, whole blood clot premeability and fibrinolysis.

The effects of Poloxamer 188 (0-5 mg/ml) on the permeability, turbidity, compaction, and fibrinolysis of fibrin network developed in human plasma, and on the permeability and fibrinolysis of network developed in whole blood were examined. Poloxamer 188 was found to increase network permeability and compaction in plasma. In networks in plasma, effects on the fibre mass-length ratio from turbidity and fibrinolysis with recombinant tissue plasminogen activator were small. Poloxamer did not alter the fibrinolysis with streptokinase. The increase in fibrin network permeability at low poloxamer concentrations was not attributable to an increase in fibre thickness, but results from alterations in the arrangement of fibrin fibres. Poloxamer also significantly increased the permeability of networks developed in whole blood. Studies with the platelet inhibitor cytochalasin B demonstrated that this effect in whole blood networks was partly from facilitation of platelet induced clot retraction. Poloxamer was not found to affect streptokinase induced fibrinolysis of whole blood networks. The effects of poloxamer support the hypothesis that depletion flocculation of fibrin intermediaries by soluble macromolecules is a significant determinant of network permeability. The therapeutic use of poloxamer will result in altered fibrin function in particular its permeability and mechanical stability. These alterations may contribute to its described antithrombotic and rheological effects.

Blood Coagulation↗
PubMed1987

An unclassified platelet function disorder associated with bleeding tendency.

A 7-year-old boy with a history of bleeding tendency showed a prolongation of bleeding time and a decrease in platelet adhesiveness. The platelets of the patient, however, had a normal reaction to ADP, collagen, epinephrine, arachidonic acid, bovine fibrinogen, ristocetin, A-23187 and thrombin-induced aggregation, and their shape was determined by electron microscopy to be normal. Therefore, this disorder could not be thought to belong to any known platelet dysfunction. On the other hand, an increase in clot retraction, a reversal of ATP/ADP, a decrease in beta-thromboglobulin and platelet factor 4 in the platelets, and an elevation of plasma levels of released beta-thromboglobulin from the platelets were observed in the patient. We don't know any cases with such an association of hypo- and hyperfunction of platelets.

Adenosine Diphosphate↗