Platelet aggregation, measurement

Frojmovic MM, Milton JG, Gear AL. Platelet aggregation measured in vitro by microscopic and electronic particle counting. Methods Enzymol 1989 169 134-147. 

An in vitro or ex vivo measure of drug effect, for example, mean inhibitory concentration (MIC) of an antimicrobial against bacterial culture inhibition of ADP-induced platelet aggregation with a fibrinogen receptor antagonist. 

Von beckerath N, Pogasta-Murray G, Wieczorek A Schomig A, Kastrati A, Correlation between platelet response units measured with a point-of-care test and ADP-induced platelet aggregation assessed with conventional optical aggregometry. ESC 2005 P2936 (abstract)... 

I 10 Tantry US, Bliden KR Gurbel PA. What is the best measure of thrombotic risks—pretreatment platelet aggregation, clopidogrel responsiveness, or posttreatment platelet aggregation Catheter Cardiovasc Interv 2005 66 597. 

Pharmacokinetic data were collected as well as pharmacodynamic measurements of platelet aggregation support (ristocetin cofactor activity) and cuticle wound blood flow. An important component of these studies was the suitability of the model. These models were chosen because of the biochemical deficiency of the particular factors and the parallel clinical syndromes. Such in vivo data can help in determining activity and dosing when such a product is first used in human trials. The Refacto molecule was also studied in rats and monkeys to determine its no observed adverse effect level, that was more than 10 times normal circulating levels. The major toxicity observed was the development of antibodies to the molecule that blocked activity and resulted in an acquired hemophilia syndrome. Similar findings were demonstrated when plasma-derived material was injected into monkeys [20]. 

Ammit and O Neil (1991) used a quantitative bioassay of platelet aggregation for rapid and selective measurement of platelet-activating factor. 

A new highly sensitive method to study platelet aggregation based on the measurement of mean radius or particle size makes it possible to record kinetics of formation of micro- and macro-aggregates in real time... 

The methods described below outline three dynamic adhesion/aggregation assays used to assess the in vitro and/or ex vivo efficacy of platelet antagonists (1) a viscometric-flow cytometric assay to measure shear-induced platelet-platelet aggregation in the bulk phase, (2) a perfusion chamber coupled with a computerized videomicroscopy system to visualize in real time and quantify (a) the adhesion and subsequent aggregation of platelets flowing over an immobilized substrate (e.g. extracellular matrix protein) and (b) free-flowing monocytic cell adhesion to immobilized platelets. 

Fig. 4. Technique for monitoring platelet aggregation in the partially obstructed left circumflex coronary artery of the dog. Electromagnetic flow probes measure blood flow. Partial obstruction of the coronary artery with a plastic Lexan cylinder results in episodic cyclical reductions in coronary blood flow that are due to platelet-dependent thrombus formation. Every 2-3 mm the thrombus must be mechanically shaken loose to restore blood. For detailed application of the Folts model, see Sullivan et al. (1992) Folts, Rowe (1974, 1988) and Folts et al. (1976, 1982).

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