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PubMed1990

Correlation between contractility and proliferation in human fibroblasts.

The contractile power of human fibroblasts was checked through their life span in vitro, using a plasma clot retraction test. It was found to decline with a pattern analogous to that of the different phases identifiable by the study of the kinetics of proliferation of these cells. The capacity to retract a plasma clot was higher in cells harvested during active growth than in cells harvested in resting phase. The decreased ability to retract during aging becomes apparent when cells are harvested in resting phase. Decreased retractile activity was also observed in postnatal cells as compared with embryonic cells. The results support a correlation between the initiation of DNA synthesis and the turnover of cytoskeletal elements. The data fit our previous results showing that the early proliferative disturbance during cellular senescence consists of a decline in the probability of initiating the division cycle linked to impaired cell attachment and spreading.

Cell Division↗
PubMed2000

The Pl(A2) polymorphism of integrin beta(3) enhances outside-in signaling and adhesive functions.

Genetic factors are believed to influence the development of arterial thromboses. Because integrin alpha(IIb)beta(3) plays a crucial role in thrombus formation, we analyzed receptor adhesive properties using Chinese hamster ovary and human kidney embryonal 293 cells overexpressing the Pl(A1) or Pl(A2) polymorphic forms of alpha(IIb)beta(3). Soluble fibrinogen binding was no different between Pl(A1) and Pl(A2) cells, either in a resting state or when alpha(IIb)beta(3) was activated with anti-LIBS6. Pl(A1) and Pl(A2) cells bound equivalently to immobilized fibronectin. In contrast, significantly more Pl(A2) cells bound to immobilized fibrinogen in an alpha(IIb)beta(3)-dependent manner than did Pl(A1) cells. Disruption of the actin cytoskeleton by cytochalasin D abolished the increased binding of Pl(A2) cells. Compared with Pl(A1) cells, Pl(A2) cells exhibited a greater extent of polymerized actin and cell spreading, enhanced tyrosine phosphorylation of pp125(FAK), and greater fibrin clot retraction. These adhesion differences appear to depend on a signaling mechanism sensitive to receptor occupancy. Thus, the Pl(A2) polymorphism altered integrin-mediated functions of adhesion, spreading, actin cytoskeleton rearrangement, and clot retraction.

Actins↗
PubMed1978

[Structural-functional organization of hemostatic clots].

The studies were carried out to verify the hypothesis on the structural-functional organization of the hemostatic clot. For this purpose the influence of the platelets and their aggregate condition on the mechanical properties of the clot was investigated. Redistribution of platelets into aggregated, caused by addition of ADP and mixing, led to the inhibition of the clot retraction. This was reflected in the form of reduction of am on the thromboelastogram. Simultaneous recording of thrombloelastogram, coagulbbogram, and platelet degranulation demonstrated that processes of viscid metamorphosis of platelets and fibrin filaments sedimentation were followed by active clot contraction. The clot is a fibrin-platelet structure whose nodes contain blood platelets, and cells--the rest blood elements. The clot retraction takes place due to contractile properties of platelets.

Adenosine Diphosphate↗
PubMed1983

Natural defense mechanisms during ischemia.

Mechanisms are described that are known to prolong survival of ischemic myocardium. Some of these mechanisms are species-specific: collateral blood flow does not contribute to survival in rats, rabbits, and pigs but it salvages subepicardial myocardium in the dog and probably in man. The most important defense mechanism is enlargement of collaterals by growth of pre-existing smaller vessels. This process is not operative in sudden coronary occlusion but may save a substantial portion of the myocardium if occlusion occurs more slowly, i.e. several days up to a week. Experimental evidence is presented that thrombotic occlusion, clot-retraction, and partial clot lysis by endothelium can be sufficiently dynamic to allow intermittent myocardial perfusion and to permit collaterals to grow. The glycogen stores of the heart are of limited importance. They are useful for glycolytic ATP-production, the limitation is imposed by the inhibition of glycolysis in ischemia due to unfavourable pH and lack of NAD. Some beta-blockers do interfere with glycogenolysis in the heart. The cardioprotective role of adenosine needs further study. An interesting concept is the change in resistance to ischemia after repeated cycles of ischemia. It is not known at present whether repeated cycles will increase or decrease the myocyte's resistance against ischemia.

Adaptation, Physiological↗
PubMed1978

Acquired IgG antibody occurring in a thrombasthenic patient: its effect on human platelet function.

In subagglutinating amounts, an IgG antibody isolated from the plasma of a polytransfused thrombasthenic patient (L) inhibited ADP-, epinephrine-, collagen-, and thrombin-induced aggregation of normal human platelets. The inhibition of ADP-induced aggregation was strongly diminished following the prior incubation of the antibody with control human platelet stroma but not with the stroma prepared from the platelets of two different thrombasthenic patients. The IgG(L) did not affect the binding of 14C-ADP to control human platelet membranes and did not inhibit the ADP-induced shape change. Bovine factor VIIIVWF-induced agglutination and ristocetin-induced aggregation of control human platelets were not inhibited in the presence of the antibody. The IgG(L) strongly inhibited ADP-induced retraction of reptilase clot and thrombin-induced clot retraction. This antibody therefore induced a thrombasthenialike state in normal human platelets, suggesting that the antigenic site recognized by the antibody plays a central role in the later stages of the mechanism of platelet aggregation induced by physiologic aggregation-inducing agents.

Adenosine Diphosphate↗
PubMed2004

Plasma membrane Ca(2+)-ATPase (PMCA) translocates to filopodia during platelet activation.

The plasma membrane Ca(2+)-ATPase (PMCA) plays an essential role in maintaining low cytosolic Ca2+ in platelets. Recently we demonstrated that PMCA is recruited to the cytoskeleton by interacting with PDZ domains. In the present study we determined the subcellular localization of PMCA using immunofluorescence microscopy. In resting platelets PMCA was distributed over the entire plasma membrane. Upon activation with thrombin, PMCA was found in filopodia adjacent to the actin cytoskeleton. PMCA translocation to filopodia was prevented by a peptide containing the last 10 residues of PMCA4b, the predominate isoform of PMCA in platelets, which contains a known PDZ domain-binding motif and was previously shown to block association of PMCA with the cytoskeleton. Incorporation of the PMCA C-terminal peptide did not affect the rate or extent of platelet aggregation, but significantly enhanced the rate of clot retraction. These results show that PMCA association with the cytoskeleton during platelet activation results in translocation of this Ca(2+)-pump to filopodia and that this association may affect later stages of platelet activation. The consequence of PMCA translocation to filopodia is likely a reduction in the local concentration of free Ca2+ in these structures resulting in regulation of the rate of clot retraction.

Binding Sites↗
PubMed1986

Aggregation of washed platelets from non-anticoagulated human blood is not reversible.

Most of the knowledge acquired on platelet function and biochemistry has been obtained from platelets prepared from blood anticoagulated with sodium citrate. Using washed platelets from human blood (PNB) to which no anticoagulants were added, we report on responses not observed with platelets prepared from citrate-anticoagulated blood. Native blood was passed rapidly (within 5 min of venepuncture) through a Sephadex G-25/G-50 column to remove divalent ions and thus prevent coagulation. Platelets were separated from the gel-filtered blood by differential centrifugation. Responses of PNB to thrombin, collagen, calcium ionophore, ristocetin, release of 14C-5hydroxytryptamine and beta-thromboglobulin, and generation of thromboxane A2 were similar to those observed for citrated platelets. Comparison of PNB with thrombin-treated platelets, which demonstrate an increase of platelet factor 3 activity, a reduction of the adenylate energy charge and an impairment of clot retraction, indicated the absence of platelet activation. Unlike citrated platelets, however, aggregation of PNB in response to ADP was irreversible in the presence of Ca2+ and fibrinogen, even at concentrations as low as 0.2 microM ADP, with aggregation taking up to 25 times longer to reach the same extent of aggregation as for citrated platelets. PNB did not aggregate to epinephrine even in the presence of Ca2+ and fibrinogen. Sodium citrate impaired ADP-induced aggregation and clot retraction of PNB. Thus citrate affects platelet function and may cause changes resulting in the unphysiological behaviour and responses of platelets.

Adenosine Diphosphate↗
PubMed1983

Heparin-dipyridamole (Persantin) treatment in pregnancy: effect on blood coagulation parameters.

13 patients suspected of intra-uterine growth retardation (IUGR) were treated with a combination of heparin and dipyridamole. The effect of this anticoagulant therapy on platelet count, clot retraction, fibrinogen degradation products, antithrombin III (AT-III), plasminogen, fibrinogen and platelet aggregation induced by epinephrine, ADP, collagen and ristocetin has been examined. All parameters were measured both before and after treatment with heparin-dipyridamole. The results were compared with the results from a control group consisting of pregnant women of the same gestational age using no medication and not suspected of IUGR (n = 17). A significant decrease in the clot retraction was observed in patients with IUGR as compared to pregnant controls (p less than 0.05). A significant decrease in the AT-III level (p less than 0.01) and a significant increase (p less than 0.01) in the fibrinogen level were observed after heparin-dipyridamole treatment of patients suspected of IUGR. We conclude that the combination of a high fibrinogen and a low AT-III level will cause an increased risk for the development of thrombosis upon termination of treatment. We also observed that heparin clearance is increased during pregnancy.

Adolescent↗
PubMed2026

Tanshinone IIA impairs platelet function and thrombus formation.

BACKGROUND: Tanshinone IIA (T-IIA) is a fat-soluble active ingredient derived from the traditional Chinese medicine Danshen and possesses cardioprotective property. However, its exact role in platelet function is unknown. OBJECTIVES: This study investigated T-IIA's role in platelet aggregation, granules release, spreading, clot retraction, as well as in vivo hemostasis and thrombus formation. METHODS: Human platelets were treated with different doses of T-IIA (10, 50, and 100 μM) to measure platelet function and activation. In addition, T-IIA was administrated into wild-type mice to evaluate hemostasis and thrombus formation. RESULTS: T-IIA significantly impaired platelet aggregation, adenosine triphosphate secretion, P-selectin expression, and spreading and clot retraction dose dependently without affecting the expression profiles of αIIbβ3 and glycoprotein VI or Ibα. Administration of T-IIA significantly prolonged mice tail bleeding time and inhibited arterial and venous thrombosis. Further analysis showed that T-IIA dose dependently reduced platelet reactive oxygen species generation. Quantitative proteomic and phosphoproteimic assays analyzing T-IIA-treated vs vehicle-treated platelets after stimulation identified dysregulated phosphorylation of several proteins, which were enriched in platelet activation. Among the downregulated phosphoproteins, Rho-associated protein kinase (ROCK)1, integrin β3, and talin1 exhibited the lower fold change of phosphorylation in T-IIA-treated platelets compared with those in vehicle-treated platelets. Consistently, T-IIA treatment inhibited the phosphorylation of ROCK1, p47phox, integrin β3, and talin1 in activated platelets. CONCLUSION: T-IIA impairs platelet function and thrombosis via inhibition of several signaling pathways including ROCK1/p47phox, β3, and talin1, implying that T-IIA may represent a promising therapeutic candidate for treating thrombotic diseases.

Animals↗
PubMed2006

Antiplatelet and antithrombotic activities of essential oil from wild Ocotea quixos (Lam.) Kosterm. (Lauraceae) calices from Amazonian Ecuador.

Ocotea quixos essential oil was shown to possess significant inhibitory activity of platelet aggregation and clot retraction in rodent plasma. This study is aimed at fully characterizing the antiplatelet activity of the whole essential oil and its main components trans-cinnamaldehyde and methyl cinnamate also in human plasma, at investigating the mechanism underlying such activity and at evaluating the potential antithrombotic activity of subacute treatment of mice with Ocotea essential oil. In vitro Ocotea essential oil and trans-cinnamaldehyde inhibited arachidonic acid-, U46619-, ADP-, phorbol12-myristate13-alcetate-, collagen-induced platelet aggregation and thrombin-induced clot retraction in human and rodent plasma; Ocotea oil and trans-cinnamaldehyde competitively antagonized contractions induced by thromboxane A2 receptor agonist U46619 in rat isolated aortic ring (K(B) = 18 and 3.2 microg ml(-1), respectively). In vivo Ocotea oil, orally administered in a subacute treatment (30-100 mg kg(-1) day(-1) for 5 days) to mice, prevented acute thrombosis induced by collagen-epinephrine intravenous injection. This antithrombotic activity was not accompanied by pro-haemorragic side effect, as detected by the inactivity in bleeding test, thus showing a favourable safety profile compared to the conventional antiplatelet agent, acetylsalicylic acid. Present findings indicate that Ocotea essential oil possesses potent and safe antithrombotic activity attributable to its antiplatelet and vasorelaxant effects. The main constituent trans-cinnamaldehyde seems to be the primary responsible for this activity through a putative mechanism involving the inhibition of thromboxane A2 receptors.

Acrolein↗
PubMed1985

Increased retraction of fibrin clots by endothelial cells of infants of diabetic mothers.

Cultured endothelial cells (EC) from the umbilical veins of infants of non-diabetic mothers induced retraction of fibrin clots formed by addition of thrombin to cell-free plasma. Fibrin clot retraction activity increased with time, reaching a maximum within 24 hours and was inhibited at 4 degrees C or in the presence of EDTA. This retraction had many characteristics in common with that induced by platelets. EC obtained from the umbilical veins of infants of poorly controlled insulin dependent diabetic mothers (IDDM) showed similar patterns of retraction. However, compared to normals, these cells induced greater retraction. Since the retraction of fibrin clots is thought to promote the exposure of sub-endothelial layers and since such an exposure plays a major role in thrombogenesis, we suggest that retraction of fibrin clot by EC should be taken into account in evaluating pre-thrombotic states.

Cells, Cultured↗
PubMed1995

Glycoprotein IIb/IIIa blockade inhibits platelet-mediated force development and reduces gel elastic modulus.

The effects of GPIIb/IIIa blockade on clot retraction were studied utilizing an instrument which directly measures force produced by platelets. GPIIb/IIIa disruption by calcium chelation, and GPIIb/IIIa blockade by peptides and anti-GPIIb/IIIa antibodies were investigated. One mM EDTA suppressed ADP-induced platelet aggregation by 72% and reduced force developed at 1200 s by 33%. At 234 microM, the tetrapeptide Arg-Gly-Asp-Ser (RGDS) suppressed platelet aggregation by 74%, reduced force at 1200 s by 45% and reduced gel elastic modulus by 19%. At 10 microM, the peptide D-Arg-Gly-L-Asp-L-Try (D-RGDW) completely suppressed platelet aggregation, reduced force development by 38% and reduced gel elastic modulus by 29%. At 0.133 microM, monoclonal anti-GPIIIa antibody (AP-3) reduced force development by 74% and reduced gel modulus by 60%. Murine antiGPIIb/IIIa antibodies 10E5 and 7E3 markedly suppressed force development. At 0.133 microM, 10E5 reduced force by 89% and reduced gel modulus by 67%. At 0.053 microM, 7E3 completely stopped force development and reduced gel modulus by 46%. Platelet aggregation was blocked by 0.027 microM 7E3. Selective GPIIb blockade by antibodies did not affect force development. None of the agents studied altered fibrin structure as monitored by effects of fibrin mass/length ratios. Suppression of platelet aggregation occurred at inhibitor concentrations substantially lower than those required to suppress force development. Complete suppression of platelet aggregation did not assure inhibition of clot retraction probably due to profound platelet activation by thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Tyrosine kinases regulate the cytoskeletal attachment of integrin alpha IIb beta 3 (platelet glycoprotein IIb/IIIa) and the cellular retraction of fibrin polymers.

Integrins promote cell-substratum and cell-cell adhesion by acting as transmembrane linker molecules between extracellular adhesion proteins and the actin-rich cytoskeleton. The integrin alpha IIb beta 3 (platelet glycoprotein IIb/IIIa) is essential for platelet spreading, aggregation, fibrin clot retraction, and for the transduction of extracellular signals. We examined the effect of the specific tyrosine kinase inhibitor herbimycin A on integrin and cytoskeletal-mediated events in thrombin-stimulated platelets. Incubation of washed platelets for 24 h with herbimycin A (5 microM) abolished the thrombin-stimulated cytoskeletal enzyme activity of pp60c-src in parallel with a reduction in the tyrosine phosphorylation of multiple platelet proteins, as assessed with anti-phosphotyrosine immunoblots. However, thrombin-induced activation of protein kinase C and the production of thromboxane A2 were not altered by herbimycin A. Despite the absence of cytoskeletal pp60c-src enzyme activity, platelet shape change, aggregation, and serotonin release were unaltered following platelet stimulation with thrombin (0.05-1.0 unit/ml). Herbimycin A-treated platelets also demonstrated normal platelet aggregation in response to collagen (5 micrograms/ml), ionophore A23187 (2 microM), and ADP/adrenaline (10 microM each). However, the ability of herbimycin A-treated platelets to retract fibrin gels was significantly reduced. This defect in clot retraction was associated with reduced incorporation of integrin alpha IIb beta 3 into the cytoskeletal fraction of thrombin-aggregated platelets. Our studies suggest that tyrosine kinases in platelets regulate the cytoskeletal attachment of alpha IIb beta 3, as an essential process for the transmission of cellular contractile forces to fibrin polymers.

Benzoquinones↗