Adaptive phasf/delay estimation for lead/ lag phase shifts

1989 ◽  
Author(s):  
F.F. Yassa ◽  
K.B. Welles
Keyword(s):  
Phase Shifts ◽  
Delay Estimation ◽  
Lag Phase

Dose-Response Aggregometry in Maternal/Neonatal Platelets

1988 ◽  
Vol 60 (02) ◽  
pp. 314-318 ◽  
Author(s):  
A M A Gader ◽  
H Bahakim ◽  
F A Jabbar ◽  
A L Lambourne ◽  
T H Gaafar ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Dose Response ◽  
Lag Phase ◽  
Phase Slope ◽  
Multiple Doses ◽  
Nonpregnant Adult ◽  
Aggregation Of Platelets

SummaryThe aggregation of platelets collected from maternal/neonatal pairs (n = 240) at the time of childbirth, was studied in response to multiple doses of ADP, collagen, arachidonic acid and ristocetin. Similar responses were obtained from healthy nonpregnant adult controls for comparison. The lag phase, slope of the aggregation curves as well as maximum aggregation (MA%) were recorded and analysed. Neonatal and adult platelets exhibited more enhanced responses to decreasing doses of ADP, arachidonic acid and ristocetin, than maternal platelets. These enhanced responses were exhibited more consistantly in the slopes of the aggregation curves than in MA%. Although neonatal platelets have shown longer lag phase in their responses to collagen, the rate of the aggregation reaction was significantly faster than maternal platelets, with no differences in MA%. These results contradict many previous reports suggesting impaired aggregation responses of neonatal platelets to these agonist. The possible reasons for these contradictions were discussed.

Conditions Affecting the Responses of Human Platelets to Epinephrine

1988 ◽  
Vol 60 (02) ◽  
pp. 209-216 ◽  
Author(s):  
Chantal Lalau Keraly ◽  
Raelene L Kinlough-Rathbone ◽  
Marian A Packham ◽  
Hidenori Suzuki ◽  
J Fraser Mustard
Keyword(s):  
Platelet Rich Plasma ◽  
Shape Change ◽  
Human Platelets ◽  
Dense Granule ◽  
Primary Phase ◽  
Lag Phase ◽  
Acid Citrate Dextrose ◽  
Two Phases ◽  
Citrate Dextrose ◽  
Thromboxane Formation

SummaryConditions affecting the responses of human platelets to epinephrine were examined. In platelet-rich plasma prepared from blood anticoagulated with hirudin or PPACK (D-pheny- lalanyl-L-prolyl-L-arginine chloromethyl ketone), epinephrine did not cause shape change or aggregation. In a Tyrode-albumin- apyrase solution containing a concentration of Ca2+ in the physiological range, and fibrinogen, epinephrine in concentrations as high as 40 μM did not induce platelet shape change, caused either no primary aggregation or very slight primary aggregation, and did not induce thromboxane formation, release of dense granule contents, or secondary aggregation. In contrast, in citrated platelet-rich plasma, epinephrine induced two phases of aggregation. This is not attributable to the generation of traces of thrombin since the same effects were evident when blood was taken into a combined citrate-hirudin anticoagulant or a combined citrate-PPACK anticoagulant. In a modified Tyrode-albu- min-apyrase solution containing approximately 20 μM Ca2+, 1 mM Mg2+, and fibrinogen, epinephrine induced extensive aggregation after a lag phase, but no primary phase was evident; thromboxane formation and release of dense granule contents accompanied the aggregation response. These responses were also observed when PPACK was included with the acid-citrate- dextrose anticoagulant, and in the washing and resuspending fluids. In the presence of aspirin or the thromboxane receptor blocker BM 13.177 a few small aggregates were detected by particle counting and by scanning electron microscopy; with the latter inhibitor, the platelets in the aggregates retained their disc shape; secondary aggregation and the responses associated with it did not occur. Thus thromboxane A2 formation is not necessary for the formation of these small aggregates, but is required for extensive aggregation and release. As with other weak agonists, the close platelet-to-platelet contact in the low Ca2+ medium appears to be necessary for full secondary aggregation. Omission of fibrinogen from the low Ca2+ medium prevented both primary and secondary aggregation in response to epinephrine. An antibody (10E5) to the glycoprotein Ilb/IIIa complex was completely inhibitory in the presence of fibrinogen. Thus the response of human platelets to epinephrine is influenced by the concentration of Ca2+ and the presence of fibrinogen in the medium in which they are suspended.

Effect of Glycosaminoglycans on Thrombin- and Atroxin-Induced Fibrin Assembly and Structure

1989 ◽  
Vol 62 (04) ◽  
pp. 1057-1061 ◽  
Author(s):  
Marcus E Carr ◽  
Patrick L Powers
Keyword(s):  
Chondroitin Sulfate ◽  
Fiber Diameter ◽  
Lag Phase ◽  
Low Molecular Weight ◽  
Fibrin Gels ◽  
Fiber Size ◽  
Induced Changes ◽  
The Impact ◽  
Fiber Radius ◽  
Turbidity Increase

SummaryThis study was performed to quantitate the impact of several glycosaminoglycans (GAG) on fibrin assembly and structure. Gel formation was monitored as the increase in optical density at 633 nm subsequent to thrombin (2 NIH u/ml) or atroxin (0.10 mg/ml) addition to solutions of buffered fibrinogen (1 mg/ml) or plasma. Gel absorbance was measured as a function of wavelength (400 to 800 nm) and gel fiber diameter and mass/length ratio (μ) were calculated. Chondroitin sulfate A (CSA)shortened the lag phase, enhanced the maximal rate of turbidity increase, and increased the final gel turbidity of fibrin gels formed by thrombin or atroxin. CSA (16 mg/ml) increased fiber μ from 1.3 to 3.1 × 1013 dalton/cm and fiber radius from 6.0 to 8.6 × 10-6 cm in thrombin-induced gels. μ increased from 0.7 to 2.7 × 1013 dalton/cm and fiber radius from 4 to 7.8 × 10-6 cm for atroxin-induced gels. Above 16 mg/ml, CSA caused fibrinogen precipitation in purified solutions but not in plasma. CSA inhibited thrombin-induced plasma clotting of plasma but effects in atroxin-mediated plasma gels paralleled those seen in purified solutions. Chondroitin sulfate B (CSB)-induced changes in fibrin were similar but slightly less dramatic than those seen with CSA. μ increased from 0.9 to 2.0 × 1013 dalton/cm for thrombin-induced fibrin gels and from 0.8 to 2.3 × 1013 dalton/cm for atroxininduced gels. Low molecular weight heparin (Mr = 5100) slowed fibrin assembly and reduced fiber size by 50% in thrombininduced gels. Changes in μ of atroxin-induced gels were much less pronounced (<20%). This study documents pronounced GAGinduced changes in fibrin structure which vary with GAG species and may mediate significant physiologic functions.

Heparin and Low Molecular Weight Heparins Inhibit Prothrombinase Formation but not its Activity in Plasma

1994 ◽  
Vol 72 (06) ◽  
pp. 862-868 ◽  
Author(s):  
Frederick A Ofosu ◽  
J C Lormeau ◽  
Sharon Craven ◽  
Lori Dewar ◽  
Noorildan Anvari
Keyword(s):  
Factor Xa ◽  
Catalytic Efficiency ◽  
Thrombin Inhibitor ◽  
Lag Phase ◽  
Factor V ◽  
Factor X ◽  
Normal Plasma ◽  
Plasma Factor ◽  
Prothrombin Activation ◽  
Plasma Heparin

SummaryFactor V activation is a critical step preceding prothrombinase formation. This study determined the contributions of factor Xa and thrombin, which activate purified factor V with similar catalytic efficiency, to plasma factor V activation during coagulation. Prothrombin activation began without a lag phase after a suspension of coagulant phospholipids, CaCl2, and factor Xa was added to factor X-depleted plasma. Hirudin, a potent thrombin inhibitor, abrogated prothrombin activation initiated with 0.5 and 1.0 nM factor Xa, but not with 5 nM factor Xa. In contrast, hirudin did not abrogate prothrombin activation in plasmas pre-incubated with 0.5,1.0 or 5 nM α-thrombin for 10 s followed by the coagulant suspension containing 0.5 nM factor Xa. Thus, thrombin activates plasma factor V more efficiently than factor Xa. At concentrations which doubled the clotting time of contact-activated normal plasma, heparin and three low Mr heparins also abrogated prothrombin activation initiated with 0.5 nM factor Xa, but not with 5 nM factor Xa. If factor V in the factor X-depleted plasma was activated (by pre-incubation with 10 nM a-thrombin for 60 s) before adding 0.5,1.0, or 5 nM factor Xa, neither hirudin nor the heparins altered the rates of prothrombin activation. Thus, none of the five anticoagulants inactivates prothrombinase. When 5 or 10 pM relipidated r-human tissue factor and CaCl2 were added to normal plasma, heparin and the three low Mr heparins delayed the onset of prothrombin activation until the concentration of factor Xa generated exceeded 1 nM, and they subsequently inhibited prothrombin activation to the same extent. Thus, hirudin, heparin and low Mr heparins suppress prothrombin activation solely by inhibiting prothrombinase formation.

Functional Properties of p-Anisoylated Plasmin-Staphylokinase Complex

1993 ◽  
Vol 70 (02) ◽  
pp. 326-331 ◽  
Author(s):  
H R Lijnen ◽  
B Van Hoef ◽  
R A G Smith ◽  
D Collen
Keyword(s):  
Human Plasma ◽  
Rate Constant ◽  
Time Course ◽  
Bolus Injection ◽  
Similar Rate ◽  
Clot Lysis ◽  
Lag Phase ◽  
Plasma Clot ◽  
Rapid Clearance ◽  
Stoichiometric Complex

SummaryThe kinetic and fibrinolytic properties of a reversibly acylated stoichiometric complex between human plasmin and recombinant staphylokinase (plasmin-STAR complex) were evaluated. The acylation rate constant of plasmin-STAR by p-amidinophenyl-p’-anisate-HCI was 52 M-1 s-1 and its deacylation rate constant 1.2 × 10-4 s-1 (t½ of 95 min) which are respectively 50-fold and around 3-fold lower than for the plasmin-streptokinase complex. The acylated complex was stable as evidenced by binding to lysine-Sepharose. However, following an initial short lag phase, the acylated plasmin-STAR complex activated plasminogen at a similar rate as the unblocked complex, whereas the acylated plasmin-streptokinase complex did not activate plasminogen. These findings indicate that STAR, unlike streptokinase, dissociates from its acylated complex with plasmin in the presence of excess plasminogen. In agreement with this hypothesis, the time course of the lysis of a 125I-fibrin labeled plasma clot submerged in citrated human plasma, is similar for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR (50% clot lysis in 2 h requires 12 nM of each agent). The plasma clearances of STAR-related antigen following bolus injection in hamsters were 1.0 to 1.5 ml/min for acylated plasmin-STAR, unblocked plasmin-STAR and free STAR, as a result of short initial half-lives of 2.0 to 2.5 min.The dissociation of the anisoylated plasmin-STAR complex and its consequent rapid clearance suggest that it has no apparent advantages as compared to free STAR for clinical thrombolysis.

The Formation of Intermediate Product I in a Purified System The Role of Factor IX or of its Precursor and of a Hageman Factor-PTA Fraction

1961 ◽  
Vol 6 (02) ◽  
pp. 224-234 ◽  
Author(s):  
E. T Yin ◽  
F Duckert
Keyword(s):  
Intermediate Product ◽  
Factor Ix ◽  
Assay Method ◽  
Lag Phase ◽  
Factor X ◽  
Haemophilia B ◽  
Hageman Factor ◽  
One Stage ◽  
The One

Summary1. The role of two clot promoting fractions isolated from either plasma or serum is studied in a purified system for the generation of intermediate product I in which the serum is replaced by factor X and the investigated fractions.2. Optimal generation of intermediate product I is possible in the purified system utilizing fractions devoid of factor IX one-stage activity. Prothrombin and thrombin are not necessary in this system.3. The fraction containing factor IX or its precursor, no measurable activity by the one-stage assay method, controls the yield of intermediate product I. No similar fraction can be isolated from haemophilia B plasma or serum.4. The Hageman factor — PTA fraction shortens the lag phase of intermediate product I formation and has no influence on the yield. This fraction can also be prepared from haemophilia B plasma or serum.

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